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Sample records for pore size distributions

  1. Pore size distribution and accessible pore size distribution in bituminous coals

    SciTech Connect

    Sakurovs, Richard; He, Lilin; Melnichenko, Yuri B; Radlinski, Andrzej Pawell; Blach, Tomasz P

    2012-01-01

    The porosity and pore size distribution of coals determine many of their properties, from gas release to their behavior on carbonization, and yet most methods of determining pore size distribution can only examine a restricted size range. Even then, only accessible pores can be investigated with these methods. Small-angle neutron scattering (SANS) and ultra small-angle neutron scattering (USANS) are increasingly used to characterize the size distribution of all of the pores non-destructively. Here we have used USANS/SANS to examine 24 well-characterized bituminous and subbituminous coals: three from the eastern US, two from Poland, one from New Zealand and the rest from the Sydney and Bowen Basins in Eastern Australia, and determined the relationships of the scattering intensity corresponding to different pore sizes with other coal properties. The range of pore radii examinable with these techniques is 2.5 nm to 7 {micro}m. We confirm that there is a wide range of pore sizes in coal. The pore size distribution was found to be strongly affected by both rank and type (expressed as either hydrogen or vitrinite content) in the size range 250 nm to 7 {micro}m and 5 to 10 nm, but weakly in intermediate regions. The results suggest that different mechanisms control coal porosity on different scales. Contrast-matching USANS and SANS were also used to determine the size distribution of the fraction of the pores in these coals that are inaccessible to deuterated methane, CD{sub 4}, at ambient temperature. In some coals most of the small ({approx} 10 nm) pores were found to be inaccessible to CD{sub 4} on the time scale of the measurement ({approx} 30 min - 16 h). This inaccessibility suggests that in these coals a considerable fraction of inherent methane may be trapped for extended periods of time, thus reducing the effectiveness of methane release from (or sorption by) these coals. Although the number of small pores was less in higher rank coals, the fraction of total

  2. Pore-size-distribution of cationic polyacrylamide hydrogels. Progress report

    SciTech Connect

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga`s mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  3. Pore-size-distribution of cationic polyacrylamide hydrogels

    SciTech Connect

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga's mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  4. Nanofiltration membranes with narrowed pore size distribution via pore wall modification.

    PubMed

    Du, Yong; Lv, Yan; Qiu, Wen-Ze; Wu, Jian; Xu, Zhi-Kang

    2016-06-30

    We propose a novel strategy for narrowing down the pore size distribution of ready-made nanofiltration membranes (NFMs) via pore wall modification. NFMs were subjected to the filtration of a highly reactive molecule solution, during which large pores were selectively reduced in size. The as-treated NFMs have high monovalent ion/divalent ion selectivity. PMID:27321407

  5. Porosity, pore size distribution and in situ strength of concrete

    SciTech Connect

    Kumar, Rakesh; Bhattacharjee, B

    2003-01-01

    In this study, in situ strength of concrete was determined through compression test of cores drilled out from laboratory cast beams. The apparent porosity and pore size distribution of the same concrete were determined through mercury intrusion porosimetry, performed on small-drilled cores. The normal-strength concrete mixes used in the experimental investigation were designed to exhibit a wide variation in their strengths. To ensure further variation in porosity, pore size distribution and strength, two modes of compaction, two varieties of coarse aggregates, different levels of age, curing period and exposure condition of concrete were also introduced in experimental scheme. With the data so generated, an appraisal of the most frequently referred relationships involving strength, porosity and pore size of cement-based materials was carried out. Finally, a new empirical model relating the in situ strength of concrete with porosity, pore size characteristics, cement content, aggregate type, exposure conditions, etc., is presented.

  6. Mechanical properties, pore size distribution, and pore solution of fly ash-belite cement mortars

    SciTech Connect

    Guerrero, A.; Goni, S.; Macias, A.; Luxan, M.P.

    1999-11-01

    The mechanical properties, pore size distribution, and extracted pore solution of fly ash-belite cement (FABC) mortars were studied for a period of 200 days. The influence of the calcination temperature, which ranged from 700 to 900 C, of the fly ash-belite cement was discussed. The evolution with hydration time of the pore size distribution was followed by mercury intrusion porosimetry, and the results correlated with those of flexural and compressive strength. The pore solution was expressed and analyzed at different times of hydration.

  7. Pore-size distributions of N-isopropylacrylamide (NIPA) hydrogels

    SciTech Connect

    Walther, D.H.; Blanch, H.W.; Prausnitz, J.M. |

    1993-11-01

    Pore-size distributions have been measured for N-isopropylacrylamide (NIPA) hydrogels at 25 and 32{degrees}C with swelling capacities 11.3 and 6.0 g swollen gel per g dry gel. The mixed-solute-exclusion method (introduced by Kuga) was used to obtain the experimental solute-exclusion curve which represents the amount of imbibed liquid inside the gel inaccessible for a solute of radius r. The pore-size distributions were obtained by using Casassa`s Brownian-motion model and numerically solving the Fredholm integral equation. The pore-size distributions of temperature-sensitive NIPA hydrogels are strongly dependent on temperature which determines swelling capacity. With increasing swelling capacity (from 6.0 to 11.3), the pore-size distribution shifts to higher mode values (27.3 to 50.6 {angstrom}) and to higher variance (1.07{center_dot}10{sup 3} to 3.58{center_dot}10{sup 3} {angstrom}{sup 2}).

  8. Using radial NMR profiles to characterize pore size distributions

    NASA Astrophysics Data System (ADS)

    Deriche, Rachid; Treilhard, John

    2012-02-01

    Extracting information about axon diameter distributions in the brain is a challenging task which provides useful information for medical purposes; for example, the ability to characterize and monitor axon diameters would be useful in diagnosing and investigating diseases like amyotrophic lateral sclerosis (ALS)1 or autism.2 Three families of operators are defined by Ozarslan,3 whose action upon an NMR attenuation signal extracts the moments of the pore size distribution of the ensemble under consideration; also a numerical method is proposed to continuously reconstruct a discretely sampled attenuation profile using the eigenfunctions of the simple harmonic oscillator Hamiltonian: the SHORE basis. The work presented here extends Ozarlan's method to other bases that can offer a better description of attenuation signal behaviour; in particular, we propose the use of the radial Spherical Polar Fourier (SPF) basis. Testing is performed to contrast the efficacy of the radial SPF basis and SHORE basis in practical attenuation signal reconstruction. The robustness of the method to additive noise is tested and analysed. We demonstrate that a low-order attenuation signal reconstruction outperforms a higher-order reconstruction in subsequent moment estimation under noisy conditions. We propose the simulated annealing algorithm for basis function scale parameter estimation. Finally, analytic expressions are derived and presented for the action of the operators on the radial SPF basis (obviating the need for numerical integration, thus avoiding a spectrum of possible sources of error).

  9. Evolution of pore size distribution during sintering of oxide nuclear fuel

    NASA Astrophysics Data System (ADS)

    Baranov, V. G.; Devyatko, Y. N.; Tenishev, A. V.; Mikhalchik, V. V.; Khomyakov, O. V.

    2016-04-01

    Uranium dioxide pellets were sintered at various temperature routes and atmospheres with different oxygen content. Statistically calculated pore size distribution of the sintered pellets and distribution function was obtained. It is shown that the average pore size is almost unchanged at intermediate stage of sintering while the total number of pores reduced.

  10. Prediction of Hydraulic Conductivity as Related to Pore Size Distribution in Unsaturated Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil pore volume as well as pore size, shape, type (i.e. biopore versus crack), continuity, and distribution in soil affect soil water and gas exchange. Vertical and lateral drainage of water by gravitational forces occurs through large, non-capillary soil pores, but redistribution and upward moveme...

  11. Modelling mass transport through a porous partition: Effect of pore size distribution

    NASA Astrophysics Data System (ADS)

    Khayet, Mohamed; Velázquez, Armando; Mengual, Juan I.

    2004-09-01

    Direct contact membrane distillation process has been studied using microporous polytetrafluoroethylene and polyvinylidene fluoride membranes. The membranes were characterized in terms of their non-wettability, pore size distribution and porosity. The mean pore sizes and pore size distributions were obtained by means of wet/dry flow method. The mean pore size and the effective porosity of the membranes were also determined from the gas permeation test. A theoretical model that considers the pore size distribution together with the gas transport mechanisms through the membrane pores was developed for this process. The contribution of each mass transport mechanism was analyzed. It was found that both membranes have pore size distributions in the Knudsen region and in the transition between Knudsen and ordinary diffusion region. The transition region was the major contribution to mass transport. The predicted water vapor permeability of the membranes were compared with the experimental ones. The effect of considering pore size distribution instead of mean pore size to predict the water vapor permeability of the membranes was investigated.

  12. Pore size distribution of shaley rock by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Hall, P. L.; Mildner, D. F. R.; Borst, R. L.

    1983-08-01

    Information concerning pore microstructure of shaly rocks is of considerable relevance to petroleum exploration and production. Pore sizes and distributions within shaly samples have been determined by small angle neutron scattering. The data are indicative of a considerable spread of pore dimension, showing inhomogeneities with a range from 20 Å and greater. The cumulative pore volumes are compared with those derived from mercury intrusion porosimetry and nitrogen adsorption and desorption isotherms.

  13. Pore size distribution of shaly rock by small angle neutron scattering

    SciTech Connect

    Hall, P.L.; Mildner, D.F.R.; Borst, R.L.

    1983-08-01

    Information concerning pore microstructure of shaly rocks is of considerable relevance to petroleum exploration and production. Pore sizes and distributions within shaly samples have been determined by small angle neutron scattering. The data are indicative of a considerable spread of pore dimension, showing inhomogeneities with a range from 20 A and greater. The cumulative pore volumes are compared with those derived from mercury intrusion porosimetry and nitrogen adsorption and desorption isotherms.

  14. Unified method for the total pore volume and pore size distribution of hierarchical zeolites from argon adsorption and mercury intrusion.

    PubMed

    Kenvin, Jeffrey; Jagiello, Jacek; Mitchell, Sharon; Pérez-Ramírez, Javier

    2015-02-01

    A generalized approach to determine the complete distribution of macropores, mesopores, and micropores from argon adsorption and mercury porosimetry is developed and validated for advanced zeolite catalysts with hierarchically structured pore systems in powder and shaped forms. Rather than using a fragmented approach of simple overlays from individual techniques, a unified approach that utilizes a kernel constructed from model isotherms and model intrusion curves is used to calculate the complete pore size distribution and the total pore volume of the material. An added benefit of a single full-range pore size distribution is that the cumulative pore area and the area distribution are also obtained without the need for additional modeling. The resulting complete pore size distribution and the kernel accurately model both the adsorption isotherm and the mercury porosimetry. By bridging the data analysis of two primary characterization tools, this methodology fills an existing gap in the library of familiar methods for porosity assessment in the design of materials with multilevel porosity for novel technological applications. PMID:25603366

  15. The Effect of Mineralization on Pore-size Distribution Patterns in Sandstone

    NASA Astrophysics Data System (ADS)

    Emmanuel, S.; Ague, J. J.

    2008-12-01

    In geological media, pore-size distributions can strongly influence important physical parameters such as permeability and specific surface area. Mineralization in rock and soil often reduces the overall porosity and can also induce changes in the distribution of pore sizes. However, the way in which mineralization affects pore size is poorly understood, with relatively little data available from field-based studies. Here, we present a high-resolution profile of pore-size distributions from a variably mineralized sandstone section. The samples were obtained from a Barents Sea core in which quartz cement had preferentially precipitated around stylolite (pressure solution) interfaces; pore-size distributions were measured in 15 samples using mercury injection porosimetry. The results demonstrate that mineralization led to a reduction in porosity of around 40% in samples closest to the stylolite. However, this reduction was not uniform over the range of pore-sizes: the greatest level of porosity reduction occurred in the 10-5-10-4 m size range, while there was no discernible change in the porosity associated with smaller pores. A reactive transport model - simulating the dissolution of quartz at the stylolite interface and subsequent reprecipitation in the rock matrix - was used to predict the evolution of the porosity associated with multiple pore-sizes; the model was successfully able to reproduce the observed porosity patterns, indicating that such an approach could be integrated into efforts to model the evolution of porosity in geological formations, including during CO2 sequestration.

  16. Idealized Shale Sorption Isotherm Measurements to Determine Pore Volume, Pore Size Distribution, and Surface Area

    NASA Astrophysics Data System (ADS)

    Holmes, R.; Wang, B.; Aljama, H.; Rupp, E.; Wilcox, J.

    2014-12-01

    One method for mitigating the impacts of anthropogenic CO2-related climate change is the sequestration of CO2 in depleted gas and oil reservoirs, including shale. The accurate characterization of the heterogeneous material properties of shale, including pore volume, surface area, pore size distributions (PSDs) and composition is needed to understand the interaction of CO2 with shale. Idealized powdered shale sorption isotherms were created by varying incremental amounts of four essential components by weight. The first two components, organic carbon and clay, have been shown to be the most important components for CO2 uptake in shales. Organic carbon was represented by kerogen isolated from a Silurian shale, and clay groups were represented by illite from the Green River shale formation. The rest of the idealized shale was composed of equal parts by weight of SiO2 to represent quartz and CaCO3 to represent carbonate components. Baltic, Eagle Ford, and Barnett shale sorption measurements were used to validate the idealized samples. The idealized and validation shale sorption isotherms were measured volumetrically using low pressure N2 (77K) and CO2 (273K) adsorbates on a Quantachrome Autosorb IQ2. Gravimetric isotherms were also produced for a subset of these samples using CO2 and CH4adsorbates under subsurface temperature and pressure conditions using a Rubotherm magnetic suspension balance. Preliminary analyses were inconclusive in validating the idealized samples. This could be a result of conflicting reports of total organic carbon (TOC) content in each sample, a problem stemming from the heterogeneity of the samples and different techniques used for measuring TOC content. The TOC content of the validation samples (Eagle Ford and Barnett) was measured by Rock-Eval pyrolysis at Weatherford Laboratories, while the TOC content in the Baltic validation samples was determined by LECO TOC. Development of a uniform process for measuring TOC in the validation samples is

  17. Determination of the pore size distribution and hydraulic properties from Nuclear Magnetic Resonance relaxometry

    NASA Astrophysics Data System (ADS)

    Stingaciu, Laura R.; Weihermüller, Lutz; Haber-Pohlmeier, Sabina; Stapf, Siegfried; Vereecken, Harry; Pohlmeier, Andreas

    2010-05-01

    Known pore size distributions can be directly linked to the water retention characteristic which is essential for the prognosis of water and solute movement through the material. In our study, we evaluated the feasibility to use Nuclear Magnetic Resonance (NMR) relaxometry measurements for the characterization of pore size distribution in four porous samples with different texture and composition. Therefore, NMR T2 and T1 relaxation measurements at 6.47 MHz were carried out for three model samples (medium sand; fine sand; and a homogenous sand / kaolin clay mixture) and a natural soil. To quantify the goodness of the approach, the NMR measurements were compared in terms of cumulated pore size distribution functions and mean pore diameter with the two classical techniques based on water retention and mercury porosimetry measurements. The results showed that T1 and T2 derived mean pore size diameters are in good agreement with each other but deviate from retention curve derived ones. This is especially the case for well sorted sands with n values > 2.7. For finer materials differences are less pronounced. A short study was performed to evaluate the influence of the variations observed in the pore diameter distributions on the hydraulic properties of the samples: θS, α, and n. In conclusion, NMR T1 and T2 relaxation measurements can be used to estimate pore size distribution, mean pore diameter, as well as the retention function and corresponding hydraulic properties.

  18. Estimation of pore size distribution using concentric double pulsed-field gradient NMR.

    PubMed

    Benjamini, Dan; Nevo, Uri

    2013-05-01

    Estimation of pore size distribution of well calibrated phantoms using NMR is demonstrated here for the first time. Porous materials are a central constituent in fields as diverse as biology, geology, and oil drilling. Noninvasive characterization of monodisperse porous samples using conventional pulsed-field gradient (PFG) NMR is a well-established method. However, estimation of pore size distribution of heterogeneous polydisperse systems, which comprise most of the materials found in nature, remains extremely challenging. Concentric double pulsed-field gradient (CDPFG) is a 2-D technique where both q (the amplitude of the diffusion gradient) and φ (the relative angle between the gradient pairs) are varied. A recent prediction indicates this method should produce a more accurate and robust estimation of pore size distribution than its conventional 1-D versions. Five well defined size distribution phantoms, consisting of 1-5 different pore sizes in the range of 5-25 μm were used. The estimated pore size distributions were all in good agreement with the known theoretical size distributions, and were obtained without any a priori assumption on the size distribution model. These findings support that in addition to its theoretical benefits, the CDPFG method is experimentally reliable. Furthermore, by adding the angle parameter, sensitivity to small compartment sizes is increased without the use of strong gradients, thus making CDPFG safe for biological applications. PMID:23548563

  19. Pore size distribution, strength, and microstructure of portland cement paste containing metal hydroxide waste

    SciTech Connect

    Majid, Z.A.; Mahmud, H.; Shaaban, M.G.

    1996-12-31

    Stabilization/solidification of hazardous wastes is used to convert hazardous metal hydroxide waste sludge into a solid mass with better handling properties. This study investigated the pore size development of ordinary portland cement pastes containing metal hydroxide waste sludge and rice husk ash using mercury intrusion porosimetry. The effects of acre and the addition of rice husk ash on pore size development and strength were studied. It was found that the pore structures of mixes changed significantly with curing acre. The pore size shifted from 1,204 to 324 {angstrom} for 3-day old cement paste, and from 956 to 263 {angstrom} for a 7-day old sample. A reduction in pore size distribution for different curing ages was also observed in the other mixtures. From this limited study, no conclusion could be made as to any correlation between strength development and porosity. 10 refs., 6 figs., 3 tabs.

  20. Direct correlation of internal gradients and pore size distributions with low field NMR.

    PubMed

    Zhang, Yan; Xiao, Lizhi; Liao, Guangzhi; Blümich, Bernhard

    2016-06-01

    Internal magnetic field gradients Gint, which arise from the magnetic susceptibility difference Δχ between solid matrix and fluid in porous media relate to the pore geometry. However, this relationship is complex and not well understood. Here we correlate internal-gradient distributions to pore-size distributions directly to examine internal gradients in detail at low field NMR. The pore-size distributions were obtained by the method of Decay due to Diffusion in the Internal Field (DDIF), and the internal-gradient distributions were measured with the Carr-Purcell-Meiboom-Gill (CPMG) method. The internal-gradient-pore-size distributions correlation maps were obtained for water in packs of glass beads with different diameter and in a sandstone sample. The relationship between internal gradients and pore structure is analyzed in detail by considering the restricted diffusion of fluids in porous samples. For each case diffusion regimes are assigned by plotting normalized CPMG data and comparing the diffusion lengths, the dephasing lengths and pore diameters. In the free-diffusion limit, the correlation maps reveal the true relationship between pore structure and internal gradients so that Δχ can be approximated from the correlation maps. This limit is met most easily at low field. It provides information about porous media, which is expected to benefit the oil industry, in particular NMR well logging. PMID:27111138

  1. Direct correlation of internal gradients and pore size distributions with low field NMR

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Xiao, Lizhi; Liao, Guangzhi; Blümich, Bernhard

    2016-06-01

    Internal magnetic field gradients Gint, which arise from the magnetic susceptibility difference Δχ between solid matrix and fluid in porous media relate to the pore geometry. However, this relationship is complex and not well understood. Here we correlate internal-gradient distributions to pore-size distributions directly to examine internal gradients in detail at low field NMR. The pore-size distributions were obtained by the method of Decay due to Diffusion in the Internal Field (DDIF), and the internal-gradient distributions were measured with the Carr-Purcell-Meiboom-Gill (CPMG) method. The internal-gradient-pore-size distributions correlation maps were obtained for water in packs of glass beads with different diameter and in a sandstone sample. The relationship between internal gradients and pore structure is analyzed in detail by considering the restricted diffusion of fluids in porous samples. For each case diffusion regimes are assigned by plotting normalized CPMG data and comparing the diffusion lengths, the dephasing lengths and pore diameters. In the free-diffusion limit, the correlation maps reveal the true relationship between pore structure and internal gradients so that Δχ can be approximated from the correlation maps. This limit is met most easily at low field. It provides information about porous media, which is expected to benefit the oil industry, in particular NMR well logging.

  2. Pore size distribution in porous glass: fractal dimension obtained by calorimetry

    NASA Astrophysics Data System (ADS)

    Neffati, R.; Rault, J.

    2001-05-01

    By differential Scanning Calorimetry (DSC), at low heating rate and using a technique of fractionation, we have measured the equilibrium DSC signal (heat flow) J q 0 of two families of porous glass saturated with water. The shape of the DSC peak obtained by these techniques is dependent on the sizes distribution of the pores. For porous glass with large pore size distribution, obtained by sol-gel technology, we show that in the domain of ice melting, the heat flow Jq is related to the melting temperature depression of the solvent, Δ T m , by the scaling law: J q 0˜Δ T m - (1 + D). We suggest that the exponent D is of the order of the fractal dimension of the backbone of the pore network and we discuss the influence of the variation of the melting enthalpy with the temperature on the value of this exponent. Similar D values were obtained from small angle neutron scattering and electronic energy transfer measurements on similar porous glass. The proposed scaling law is explained if one assumes that the pore size distribution is self similar. In porous glass obtained from mesomorphic copolymers, the pore size distribution is very sharp and therefore this law is not observed. One concludes that DSC, at low heating rate ( q? 2°C/min) is the most rapid and less expensive method for determining the pore distribution and the fractal exponent of a porous material.

  3. Influence of pore size distribution on the adsorption of phenol on PET-based activated carbons.

    PubMed

    Lorenc-Grabowska, Ewa; Diez, María A; Gryglewicz, Grazyna

    2016-05-01

    The role of pore size distribution in the adsorption of phenol in aqueous solutions on polyethylene terephthalate (PET)-based activated carbons (ACs) has been analyzed. The ACs were prepared from PET and mixtures of PET with coal-tar pitch (CTP) by means of carbonization and subsequent steam and carbon dioxide activation at 850 and 950 °C, respectively. The resultant ACs were characterized on the basis of similarities in their surface chemical features and differences in their micropore size distributions. The adsorption of phenol was carried out in static conditions at ambient temperature. The pseudo-second order kinetic model and Langmuir model were found to fit the experimental data very well. The different adsorption capacities of the ACs towards phenol were attributed to differences in their micropore size distributions. Adsorption capacity was favoured by the volume of pores with a size smaller than 1.4 nm; but restricted by pores smaller than 0.8 nm. PMID:26890386

  4. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials.

    PubMed

    Félix, V; Jannot, Y; Degiovanni, A

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10(-1) to 10(5) Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent. PMID:22667640

  5. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    NASA Astrophysics Data System (ADS)

    Félix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10-1 to 105 Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  6. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    SciTech Connect

    Felix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-15

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10{sup -1} to 10{sup 5} Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  7. New general pore size distribution model by classical thermodynamics application: Activated carbon

    USGS Publications Warehouse

    Lordgooei, M.; Rood, M.J.; Rostam-Abadi, M.

    2001-01-01

    A model is developed using classical thermodynamics to characterize pore size distributions (PSDs) of materials containing micropores and mesopores. The thermal equation of equilibrium adsorption (TEEA) is used to provide thermodynamic properties and relate the relative pore filling pressure of vapors to the characteristic pore energies of the adsorbent/adsorbate system for micropore sizes. Pore characteristic energies are calculated by averaging of interaction energies between adsorbate molecules and adsorbent pore walls as well as considering adsorbate-adsorbate interactions. A modified Kelvin equation is used to characterize mesopore sizes by considering variation of the adsorbate surface tension and by excluding the adsorbed film layer for the pore size. The modified-Kelvin equation provides similar pore filling pressures as predicted by density functional theory. Combination of these models provides a complete PSD of the adsorbent for the micropores and mesopores. The resulting PSD is compared with the PSDs from Jaroniec and Choma and Horvath and Kawazoe models as well as a first-order approximation model using Polanyi theory. The major importance of this model is its basis on classical thermodynamic properties, less simplifying assumptions in its derivation compared to other methods, and ease of use.

  8. The effect of magnetic particles on pore size distribution in soft polyurethane foams

    NASA Astrophysics Data System (ADS)

    Schümann, M.; Günther, S.; Odenbach, S.

    2014-07-01

    The combination of elastomeric matrices with magnetic particles to obtain magnetically controllable hybrid materials is an actual field of intense research. An important aspect in this context is the stiffness of the matrix, which determines the effectiveness of the magnetically driven changes in the material properties. In this paper an approach has been undertaken to use soft polyurethane foams as matrix material. By means of x-ray computed microtomography and digital image processing the pore size distribution has been determined to get information on how this distribution is affected by the introduction of magnetic microparticles. To do so, 20 000 to 40 000 pores per foam sample were evaluated. As a result, it could be proven that the pore sizes of the analysed foams clearly obey the Weibull distribution. Increasing the carbonyl iron particle concentrations leads to a decrement of the shape parameter of the distribution. Based on known particle stabilization mechanisms, an approach to explain the experimental results is proposed.

  9. Direct correlation of diffusion and pore size distributions with low field NMR

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Xiao, Lizhi; Liao, Guangzhi; Song, Yi-Qiao

    2016-08-01

    The time-dependent diffusion coefficient (D) is a powerful tool to probe microstructure in porous media, and can be obtained by the NMR method. In a real porous sample, molecular diffusion is very complex. Here we present a new method which directly measures the relationship between effective diffusion coefficients and pore size distributions without knowing surface relaxivity. This method is used to extract structural information and explore the relationship between D and a in porous media having broad pore size distributions. The diffusion information is encoded by the Pulsed Field Gradient (PFG) method and the pore size distributions are acquired by the Decay due to Diffusion in the Internal Field (DDIF) method. Two model samples were measured to verify this method. Restricted diffusion was analyzed, and shows that most fluid molecules experience pore wall. The D(a) curves obtained from correlation maps were fitted to the Padé approximant equation and a good agreement was found between the fitting lines and the measured data. Then a sandstone sample with unknown structure was measured. The state of confined fluids was analyzed and structural information, such as pore size distributions, were extracted. The D - T1 correlation maps were also obtained using the same method, which yielded surface relaxivities for different samples. All the experiments were conducted on 2 MHz NMR equipment to obtain accurate diffusion information, where internal gradients can be neglected. This method is expected to have useful applications in the oil industry, particularly for NMR logging in the future.

  10. Direct correlation of diffusion and pore size distributions with low field NMR.

    PubMed

    Zhang, Yan; Xiao, Lizhi; Liao, Guangzhi; Song, Yi-Qiao

    2016-08-01

    The time-dependent diffusion coefficient (D) is a powerful tool to probe microstructure in porous media, and can be obtained by the NMR method. In a real porous sample, molecular diffusion is very complex. Here we present a new method which directly measures the relationship between effective diffusion coefficients and pore size distributions without knowing surface relaxivity. This method is used to extract structural information and explore the relationship between D and a in porous media having broad pore size distributions. The diffusion information is encoded by the Pulsed Field Gradient (PFG) method and the pore size distributions are acquired by the Decay due to Diffusion in the Internal Field (DDIF) method. Two model samples were measured to verify this method. Restricted diffusion was analyzed, and shows that most fluid molecules experience pore wall. The D(a) curves obtained from correlation maps were fitted to the Padé approximant equation and a good agreement was found between the fitting lines and the measured data. Then a sandstone sample with unknown structure was measured. The state of confined fluids was analyzed and structural information, such as pore size distributions, were extracted. The D - T1 correlation maps were also obtained using the same method, which yielded surface relaxivities for different samples. All the experiments were conducted on 2MHz NMR equipment to obtain accurate diffusion information, where internal gradients can be neglected. This method is expected to have useful applications in the oil industry, particularly for NMR logging in the future. PMID:27371788

  11. Evaluation of methods for determining the pore size distribution and pore-network connectivity of porous carbons.

    PubMed

    Cai, Q; Buts, A; Biggs, M J; Seaton, N A

    2007-07-31

    The pore size distribution (PSD) and the pore-network connectivity of a porous material determine its properties in applications such as gas storage, adsorptive separations, and catalysis. Methods for the characterization of the pore structure of porous carbons are widely used, but the relationship between the structural parameters measured and the real structure of the material is not yet clear. We have evaluated two widely used and powerful characterization methods based on adsorption measurements by applying the methods to a model carbon which captures the essential characteristics of real carbons but (unlike a real material) has a structure that is completely known. We used three species (CH4, CF4, and SF6) as adsorptives and analyzed the results using an intersecting capillaries model (ICM) which was modeled using a combination of Monte Carlo simulation and percolation theory to obtain the PSD and the pore-network connectivity. There was broad agreement between the PSDs measured using the ICM and the geometric PSD of the model carbon, as well as some systematic differences which are interpreted in terms of the pore structure of the carbon. The measured PSD and connectivity are shown to be able to predict adsorption in the model carbon, supporting the use of the ICM to characterize real porous carbons. PMID:17602506

  12. Strategies for Tailoring the Pore-Size Distribution of Virus Retention Filter Papers.

    PubMed

    Gustafsson, Simon; Mihranyan, Albert

    2016-06-01

    The goal of this work is to demonstrate how the pore-size distribution of the nanocellulose-based virus-retentive filter can be tailored. The filter paper was produced using cellulose nanofibers derived from Cladophora sp. green algae using the hot-press drying at varying drying temperatures. The produced filters were characterized using scanning electron microscopy, atomic force microscopy, and N2 gas sorption analysis. Further, hydraulic permeability and retention efficiency toward surrogate 20 nm model particles (fluorescent carboxylate-modified polystyrene spheres) were assessed. It was shown that by controlling the rate of water evaporation during hot-press drying the pore-size distribution can be precisely tailored in the region between 10 and 25 nm. The mechanism of pore formation and critical parameters are discussed in detail. The results are highly valuable for development of advanced separation media, especially for virus-retentive size-exclusion filtration. PMID:27144657

  13. Investigation of pore size and energy distributions by statistical physics formalism applied to agriculture products

    NASA Astrophysics Data System (ADS)

    Aouaini, Fatma; Knani, Salah; Yahia, Manel Ben; Bahloul, Neila; Ben Lamine, Abdelmottaleb; Kechaou, Nabil

    2015-12-01

    In this paper, we present a new investigation that allows determining the pore size distribution (PSD) in a porous medium. This PSD is achieved by using the desorption isotherms of four varieties of olive leaves. This is by the means of statistical physics formalism and Kelvin's law. The results are compared with those obtained with scanning electron microscopy. The effect of temperature on the distribution function of pores has been studied. The influence of each parameter on the PSD is interpreted. A similar function of adsorption energy distribution, AED, is deduced from the PSD.

  14. Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

    NASA Astrophysics Data System (ADS)

    Purewal, J. J.; Kabbour, H.; Vajo, J. J.; Ahn, C. C.; Fultz, B.

    2009-05-01

    Pore size distributions (PSD) and supercritical H2 isotherms have been measured for two activated carbon fiber (ACF) samples. The surface area and the PSD both depend on the degree of activation to which the ACF has been exposed. The low-surface-area ACF has a narrow PSD centered at 0.5 nm, while the high-surface-area ACF has a broad distribution of pore widths between 0.5 and 2 nm. The H2 adsorption enthalpy in the zero-coverage limit depends on the relative abundance of the smallest pores relative to the larger pores. Measurements of the H2 isosteric adsorption enthalpy indicate the presence of energy heterogeneity in both ACF samples. Additional measurements on a microporous, coconut-derived activated carbon are presented for reference.

  15. Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers.

    PubMed

    Purewal, J J; Kabbour, H; Vajo, J J; Ahn, C C; Fultz, B

    2009-05-20

    Pore size distributions (PSD) and supercritical H2 isotherms have been measured for two activated carbon fiber (ACF) samples. The surface area and the PSD both depend on the degree of activation to which the ACF has been exposed. The low-surface-area ACF has a narrow PSD centered at 0.5 nm, while the high-surface-area ACF has a broad distribution of pore widths between 0.5 and 2 nm. The H2 adsorption enthalpy in the zero-coverage limit depends on the relative abundance of the smallest pores relative to the larger pores. Measurements of the H2 isosteric adsorption enthalpy indicate the presence of energy heterogeneity in both ACF samples. Additional measurements on a microporous, coconut-derived activated carbon are presented for reference. PMID:19420660

  16. Pore size distribution calculation from 1H NMR signal and N2 adsorption-desorption techniques

    NASA Astrophysics Data System (ADS)

    Hassan, Jamal

    2012-09-01

    The pore size distribution (PSD) of nano-material MCM-41 is determined using two different approaches: N2 adsorption-desorption and 1H NMR signal of water confined in silica nano-pores of MCM-41. The first approach is based on the recently modified Kelvin equation [J.V. Rocha, D. Barrera, K. Sapag, Top. Catal. 54(2011) 121-134] which deals with the known underestimation in pore size distribution for the mesoporous materials such as MCM-41 by introducing a correction factor to the classical Kelvin equation. The second method employs the Gibbs-Thompson equation, using NMR, for melting point depression of liquid in confined geometries. The result shows that both approaches give similar pore size distribution to some extent, and also the NMR technique can be considered as an alternative direct method to obtain quantitative results especially for mesoporous materials. The pore diameter estimated for the nano-material used in this study was about 35 and 38 Å for the modified Kelvin and NMR methods respectively. A comparison between these methods and the classical Kelvin equation is also presented.

  17. Exploring the impact of pore size distribution on the performance of carbon electrodes for capacitive deionization.

    PubMed

    Han, Linchen; Karthikeyan, K G; Anderson, Marc A; Gregory, Kelvin B

    2014-09-15

    Capacitive deionization (CDI) removes charged ions from aqueous solutions through entrapment in the electric double layer (EDL) when the porous electrodes are polarized. In this study, three types of activated carbon cloth (ACC) with different pore-size distributions were used to study the effect of pore characteristics on electrosorption during CDI. Removal of seven different monovalent ions was examined for each ACC in batch reactors under 5 different combinations of applied potential and ionic strength. Results show underlying sorption mechanisms in the meso- and micro-pores were different. Electrosorption in the mesopores is influenced by partially-distorted EDL caused by EDL overlapping. Sorption capacity increased with increasing applied potential or ionic strength as overlapping effects were reduced. In contrast, EDL in the microporous regions could be highly distorted resulting in enhanced sorption capacity, which cannot be adequately described using the classic EDL theories. Electrosorption density (i.e., sorption capacity normalized by pore volume) decreased as the mesoporosity-to-microporosity ratio increased. These results are in agreement with those obtained using mathematical modeling by other recent CDI studies. Charge efficiency values were between 20% and 40% and appear to be substantially influenced by Faradaic reactions and ion desorption from the electrode surfaces. These findings suggest that pore-size distribution of electrode materials, especially the meso/microporosity ratio, should be optimized for the removal of targeted ions by CDI and well characterized to conduct more precise CDI modeling. PMID:24998059

  18. A Model for Hydraulic Properties Based on Angular Pores with Lognormal Size Distribution

    NASA Astrophysics Data System (ADS)

    Durner, W.; Diamantopoulos, E.

    2014-12-01

    Soil water retention and unsaturated hydraulic conductivity curves are mandatory for modeling water flow in soils. It is a common approach to measure few points of the water retention curve and to calculate the hydraulic conductivity curve by assuming that the soil can be represented as a bundle of capillary tubes. Both curves are then used to predict water flow at larger spatial scales. However, the predictive power of these curves is often very limited. This can be very easily illustrated if we measure the soil hydraulic properties (SHPs) for a drainage experiment and then use these properties to predict the water flow in the case of imbibition. Further complications arise from the incomplete wetting of water at the solid matrix which results in finite values of the contact angles between the solid-water-air interfaces. To address these problems we present a physically-based model for hysteretic SHPs. This model is based on bundles of angular pores. Hysteresis for individual pores is caused by (i) different snap-off pressures during filling and emptying of single angular pores and (ii) by different advancing and receding contact angles for fluids that are not perfectly wettable. We derive a model of hydraulic conductivity as a function of contact angle by assuming flow perpendicular to pore cross sections and present closed-form expressions for both the sample scale water retention and hydraulic conductivity function by assuming a log-normal statistical distribution of pore size. We tested the new model against drainage and imbibition experiments for various sandy materials which were conducted with various liquids of differing wettability. The model described both imbibition and drainage experiments very well by assuming a unique pore size distribution of the sample and a zero contact angle for the perfectly wetting liquid. Eventually, we see the possibility to relate the particle size distribution with a model which describes the SHPs.

  19. A solid with a hierarchical tetramodal micro-meso-macro pore size distribution

    PubMed Central

    Ren, Yu; Ma, Zhen; Morris, Russell E.; Liu, Zheng; Jiao, Feng; Dai, Sheng; Bruce, Peter G.

    2013-01-01

    Porous solids have an important role in addressing some of the major energy-related problems facing society. Here we describe a porous solid, α-MnO2, with a hierarchical tetramodal pore size distribution spanning the micro-, meso- and macro pore range, centred at 0.48, 4.0, 18 and 70 nm. The hierarchical tetramodal structure is generated by the presence of potassium ions in the precursor solution within the channels of the porous silica template; the size of the potassium ion templates the microporosity of α-MnO2, whereas their reactivity with silica leads to larger mesopores and macroporosity, without destroying the mesostructure of the template. The hierarchical tetramodal pore size distribution influences the properties of α-MnO2 as a cathode in lithium batteries and as a catalyst, changing the behaviour, compared with its counterparts with only micropores or bimodal micro/mesopores. The approach has been extended to the preparation of LiMn2O4 with a hierarchical pore structure. PMID:23764887

  20. Nondestructive technique for the characterization of the pore size distribution of soft porous constructs for tissue engineering.

    PubMed

    Safinia, Laleh; Mantalaris, Athanasios; Bismarck, Alexander

    2006-03-28

    Polymer scaffolds tailored for tissue engineering applications possessing the desired pore structure require reproducible fabrication techniques. Nondestructive, quantitative methods for pore characterization are required to determine the pore size and its distribution. In this study, a promising alternative to traditional pore size characterization techniques is presented. We introduce a quantitative, nondestructive and inexpensive method to determine the pore size distribution of large soft porous solids based on the on the displacement of a liquid, that spreads without limits though a porous medium, by nitrogen. The capillary pressure is measured and related to the pore sizes as well as the pore size distribution of the narrowest bottlenecks of the largest interconnected pores in a porous medium. The measured pore diameters correspond to the narrowest bottleneck of the largest pores connecting the bottom with the top surface of a given porous solid. The applicability and reproducibility of the breakthrough technique is demonstrated on two polyurethane foams, manufactured using the thermally induced phase separation (TIPS) process, with almost identical overall porosity (60-70%) but very different pore morphology. By selecting different quenching temperatures to induce polymer phase separation, the pore structure could be regulated while maintaining the overall porosity. Depending on the quenching temperature, the foams exhibited either longitudinally oriented tubular macropores interconnected with micropores or independent macropores connected to adjacent pores via openings in the pore walls. The pore size and its distribution obtained by the breakthrough test were in excellent agreement to conventional characterization techniques, such as scanning electron microscopy combined with image analysis, BET technique, and mercury intrusion porosimetry. This technique is suitable for the characterization of the micro- and macropore structure of soft porous solids

  1. Pore Size Distribution Estimates Compared: Available software applied to soil CT and synthetic images.

    NASA Astrophysics Data System (ADS)

    Houston, Alasdair N.; Falconer, Ruth E.; Otten, Wilfred; Hapca, Simona M.

    2015-04-01

    The Pore Size Distribution (PSD) has been widely used as a means of characterising porous media and, in conjunction with knowledge of pore space connectivity, has been used to infer hydrological properties. There exist various strategies to estimate PSD from a segmented image and each strategy typically involves a sequence of algorithms that transform image information. Some of these algorithms may be explicitly parameterised, requiring decisions by a knowledgeable operator. As a result PSD estimates may be quite variable between software applications and operators. In order to better understand these differences, a constrained boolean model was used to construct synthetic images whose pore structure is without ambiguity and whose properties can be analytically determined. Applying to such images a selection of analysis procedures in the form of readily available software applications, reveals differences between PSD estimates and analytic information. In some cases it is possible to attribute these differences to artifacts visible within map images generated by the analysis procedures, permitting correction procedures to be devised. In the case of soil CT images which exhibit complex interconnected pore structure, differences in the PSD estimate between analysis procedures are very great in some cases. Inspection of map images can again help in identifying the cause of such problems, but this may result from a fundamental property of the procedure with respect to complex pore structure. Based on the evidence presented, we conclude that some readily available software will produce PSD estimates that can usefully characterise geomaterials.

  2. Importance of Pore Size Distribution of Fine-grained Sediments on Gas Hydrate Equilibrium

    NASA Astrophysics Data System (ADS)

    Kwon, T. H.; Kim, H. S.; Cho, G. C.; Park, T. H.

    2015-12-01

    Gas hydrates have been considered as a new source of natural gases. For the gas hydrate production, the gas hydrate reservoir should be depressurized below the equilibrium pressure of gas hydrates. Therefore, it is important to predict the equilibrium of gas hydrates in the reservoir conditions because it can be affected by the pore size of the host sediments due to the capillary effect. In this study, gas hydrates were synthesized in fine-grained sediment samples including a pure silt sample and a natural clayey silt sample cored from a hydrate occurrence region in Ulleung Basin, East Sea, offshore Korea. Pore size distributions of the samples were obtained by the nitrogen adsorption and desorption test and the mercury intrusion porosimetry. The equilibrium curve of gas hydrates in the fine-grained sediments were found to be significantly influenced by the clay fraction and the corresponding small pores (>50 nm in diameter). For the clayey silt sample, the equilibrium pressure was higher by ~1.4 MPa than the bulk equilibrium pressure. In most cases of oceanic gas hydrate reservoirs, sandy layers are found interbedded with fine-grained sediment layers while gas hydrates are intensively accumulated in the sandy layers. Our experiment results reveal the inhibition effect of fine-grained sediments against gas hydrate formation, in which greater driving forces (e.g., higher pressure or lower temperature) are required during natural gas migration. Therefore, gas hydrate distribution in interbedded layers of sandy and fine-grained sediments can be explained by such capillary effect induced by the pore size distribution of host sediments.

  3. Permeability-Selectivity Analysis of Microfiltration and Ultrafiltration Membranes: Effect of Pore Size and Shape Distribution and Membrane Stretching.

    PubMed

    Siddiqui, Muhammad Usama; Arif, Abul Fazal Muhammad; Bashmal, Salem

    2016-01-01

    We present a modeling approach to determine the permeability-selectivity tradeoff for microfiltration and ultrafiltration membranes with a distribution of pore sizes and pore shapes. Using the formulated permeability-selectivity model, the effect of pore aspect ratio and pore size distribution on the permeability-selectivity tradeoff of the membrane is analyzed. A finite element model is developed to study the effect of membrane stretching on the distribution of pore sizes and shapes in the stretched membrane. The effect of membrane stretching on the permeability-selectivity tradeoff of membranes is also analyzed. The results show that increasing pore aspect ratio improves membrane performance while increasing the width of pore size distribution deteriorates the performance. It was also found that the effect of membrane stretching on the permeability-selectivity tradeoff is greatly affected by the uniformity of pore distribution in the membrane. Stretching showed a positive shift in the permeability-selectivity tradeoff curve of membranes with well-dispersed pores while in the case of pore clustering, a negative shift in the permeability-selectivity tradeoff curve was observed. PMID:27509528

  4. Multiscale characterization of pore size distributions using mercury porosimetry and nitrogen adsorption

    NASA Astrophysics Data System (ADS)

    Paz-Ferreiro, J.; Tarquis, A. M.; Miranda, J. G. V.; Vidal Vázquez, E.

    2009-04-01

    The soil pore space is a continuum extremely variable in size, including structures smaller than nanometres and as large as macropores or cracks with millimetres or even centimetres size. Pore size distributions (PSDs) affects important soil functions, such as those related with transmission and storage of water, and root growth. Direct and indirect measurements of PSDs are becoming increasingly used to characterize soil structure. Mercury injection porosimetry and nitrogen adsorption isotherms are techniques commonly employed for assessing equivalent pore size diameters in the range from about 50 nm to 100 m and 2 to 500 nm, respectively. The multifractal formalism was used to describe Hg injection curves and N2 adsorption isotherms from two series of a Mollisol cultivated under no tillage and minimum tillage. Soil samples were taken from 0-10, 10-20 and 20-30 cm depths in two experimental fields located in the north of Buenos Aires and South of Santa Fe provinces, Argentina. All the data sets analyzed from the two studied soil attributes showed remarkably good scaling trends as assessed by singularity spectrum and generalized dimension spectrum. Both, experimental Hg injection curves and N2 adsorption isotherms could be fitted reasonably well with multifractal models. A wide variety of singularity and generalized dimension spectra was found for the variables. The capacity dimensions, D0, for both Hg injection and N2 adsorption data were not significantly different from the Euclidean dimension. However, the entropy dimension, D1, and correlation dimension, D2, obtained from mercury injection and nitrogen adsorption data showed significant differences. So, D1 values were on average 0.868 and varied from 0.787 to 0.925 for Hg intrusion curves. Entropy dimension, D1, values for N2 adsorption isotherms were on average 0.582 significantly lower than those obtained when using the former technique. Twenty-three out of twenty-four N2 isotherms had D1 values in a

  5. Pore size distributions in microporous membranes. 1: Surface study of track-etched filters by image analysis

    SciTech Connect

    Calvo, J.I.; Hernandez, A.; Caruana, G.; Martinez, L.

    1995-10-01

    The surface morphology of several Cyclopore filters, consisting of thin track-etched sheets of polycarbonate, is analyzed here. Scanning electron microscopy and computerized image analysis have been applied. The surface porosity and the pore density or number of pores per surface unit are directly obtained for each filter, while the statistical distribution of the pore areas, pore perimeters, equivalent pore diameters, and pore shape factors are studied as well. These pore size distributions have been studied for six types of filters (C01, C02, C04, C06, C08, and C10) and the existence of a relevant portion of double and other multiple pores has been revealed. The fraction of these multiple pores are correlated with the nominal pore radii. The results on pore size have been used to predict the volume flows of the membranes studied. This can be done only by assuming that the surface characteristics remain unchanged in the internal volume of the filters, which leads to hydrodynamic radii well in accordance with the experimental ones, within the error range. Nevertheless, it seems that some of the pores should have internal widenings with inner radii close to 120% of the external ones.

  6. Jointly deriving NMR surface relaxivity and pore size distributions by NMR relaxation experiments on partially desaturated rocks

    NASA Astrophysics Data System (ADS)

    Mohnke, O.; Hughes, B.

    2014-06-01

    Nuclear magnetic resonance (NMR) relaxometry is a geophysical method widely used in borehole and laboratory applications to nondestructively infer transport and storage properties of rocks and soils as it is directly sensitive to the water/oil content and pore sizes. However, for inferring pore sizes, NMR relaxometry data need to be calibrated with respect to a surface interaction parameter, surface relaxivity, which depends on the type and mineral constituents of the investigated rock. This study introduces an inexpensive and quick alternative to the classical calibration methods, e.g., mercury injection, pulsed field gradient (PFG) NMR, or grain size analysis, which allows for jointly estimating NMR surface relaxivity and pore size distributions using NMR relaxometry data from partially desaturated rocks. Hereby, NMR relaxation experiments are performed on the fully saturated sample and on a sample partially drained at a known differential pressure. Based on these data, the (capillary) pore radius distribution and surface relaxivity are derived by joint optimization of the Brownstein-Tarr and the Young-Laplace equation assuming parallel capillaries. Moreover, the resulting pore size distributions can be used to predict water retention curves. This inverse modeling approach—tested and validated using NMR relaxometry data measured on synthetic porous borosilicate samples with known petrophysical properties (i.e., permeability, porosity, inner surfaces, pore size distributions)—yields consistent and reproducible estimates of surface relaxivity and pore radii distributions. Also, subsequently calculated water retention curves generally correlate well with measured water retention curves.

  7. Pore Size Distribution and Methane Equilibrium Conditions at Walker Ridge Block 313, Northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Bihani, A. D.; Daigle, H.; Cook, A.; Glosser, D.; Shushtarian, A.

    2015-12-01

    Coexistence of three methane phases (liquid (L), gas (G), hydrate (H)) in marine gas hydrate systems may occur according to in-situ pressure, temperature, salinity and pore size. In sediments with salinity close to seawater, a discrete zone of three-phase (3P) equilibrium may occur near the base of the regional hydrate stability zone (RHSZ) due to capillary effects. The existence of a 3P zone influences the location of the bottom-simulating reflection (BSR) and has implications for methane fluxes at the base of the RHSZ. We studied hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 in the northern Gulf of Mexico. We determined pore size distributions (PSD) by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict PSD through comparison with mercury injection capillary pressure measurements. With the computed PSD, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the 3P equilibrium zone. As in previous studies at Blake Ridge and Hydrate Ridge, the top of the 3P zone moves upwards with increasing water depth and overlies the bulk 3P equilibrium depth. In clays at Walker Ridge, the predicted thickness of the 3P zone is approximately 35 m, but in coarse sands it is only a few meters due to the difference in absolute pore sizes and the width of the PSD. The thick 3P zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.

  8. Pore size distribution and methane equilibrium conditions at Walker Ridge Block 313, northern Gulf of Mexico

    SciTech Connect

    Bihani, Abhishek; Daigle, Hugh; Cook, Ann; Glosser, Deborah; Shushtarian, Arash

    2015-12-15

    Coexistence of three methane phases (liquid (L), gas (G), hydrate (H)) in marine gas hydrate systems may occur according to in-situ pressure, temperature, salinity and pore size. In sediments with salinity close to seawater, a discrete zone of three-phase (3P) equilibrium may occur near the base of the regional hydrate stability zone (RHSZ) due to capillary effects. The existence of a 3P zone influences the location of the bottom-simulating reflection (BSR) and has implications for methane fluxes at the base of the RHSZ. We studied hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 in the northern Gulf of Mexico. We determined pore size distributions (PSD) by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict PSD through comparison with mercury injection capillary pressure measurements. With the computed PSD, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the 3P equilibrium zone. As in previous studies at Blake Ridge and Hydrate Ridge, the top of the 3P zone moves upwards with increasing water depth and overlies the bulk 3P equilibrium depth. In clays at Walker Ridge, the predicted thickness of the 3P zone is approximately 35 m, but in coarse sands it is only a few meters due to the difference in absolute pore sizes and the width of the PSD. The thick 3P zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.

  9. Pore-throat size distributions in Permo-Triassic sandstones from the United Kingdom and some implications for contaminant hydrogeology

    NASA Astrophysics Data System (ADS)

    Bloomfield, J. P.; Gooddy, D. C.; Bright, M. I.; Williams, P. J.

    2001-06-01

    Pore-throat size distributions (PSDs) from mercury injection capillary pressure (MICP) tests have been used to characterise 153 samples of Permo-Triassic sandstones from the United Kingdom. The PSDs have been parameterised using the Brooks-Corey and van Genuchten functions. Pore-throat sizes are in the range 0.01-427 µm, and dominant pore-throat sizes range from about 0.1-90 µm. Values of λ, the Brooks-Corey pore-size distribution index, range from 0.002-2.27, and values of m, the van Genuchten pore-size distribution index, range from 0.03-0.92. A number of classes of sandstone can be recognised on the basis of trends in the fitted parameters. The van Genuchten function provides the most effective method for classifying different sandstones. Additionally, a cross-plot of gas permeability against displacement pressure (derived from the van Genuchten function) shows that the data fall into two distinct sub-populations. The frequency distribution of a larger population of sandstone permeabilities can be modelled using the mean and standard deviation of the two sub-populations identified in the MICP study, assuming that the sub-populations are approximated by log-normal distributions. The distribution of sandstones with small pore-throat sizes is critical to the fate of pathogens and immiscible phase contaminants in the aquifer.

  10. Pore size distribution of a deeply excavated Oxisol after 19 years reclamation

    NASA Astrophysics Data System (ADS)

    dos Santos Batista Bonini, Carolina; de Cássia Marchini, Débora; Alves, Marlene Cristina; García de Arruda, Otton; Paz-Ferreiro, Jorge

    2013-04-01

    Digging of the local soil and using it as a raw material for construction purposes has been identified as a non-negligible source of land degradation. Techniques aimed at soil profile reconstruction and ecological restoration of soils truncated by mechanical excavation using heavy machinery have been investigated Both, total soil porosity and pore size distribution are important properties for soil management as well as for assessing the recovery of soil function after land degradation. In this way, macropores are responsible for aeration, whereas water storage depends on soil meso- and micropores in the soil and the optimal pore-size distribution is also an indicator of soil quality. We investigated the changes in the pore size distribution of a soil that was beheaded to extract raw materials after a 19 year period of reclamation, which involved the use of green manures, gypsum and pasture for the purpose of profile recovery. The studied area is located in Mato Grosso do Sul State, Brzil. A field trial was performed following a completely randomized experimental design with seven treatments and four replications. Starting 1992, the initial treatments were: 1) control (tilled bare soil), 2)Stizolobium aterrium, 3)Cajanus cajan, 4)lime+S. aterrimum, 5) lime+C. cajan, 6) lime + gypsum + S. aterrimum, 7) lime + gypsum+C. cajan. In 1994, all treatments with C. cajan were replaced by Canavalia ensiformis and in 1999, Brachiaria decumbens was implanted in all the experimental plots. Data from vegetated treatments were compared with bare soil (control) and native vegetation (Savannah). Soil samples were collected in 2011 at the 0.00-0.10, 0.10-0.20, and 0.20-0.40 m depths. Treatment differences were assessed by analysis of variance, following the Scott-Knott test (5%) of probability to compare averages. Macroporosity of the 0.00-0.10 m top layer was above the 0.10 m3m-3 threshold considered as critical for plant growth. On the 0.10-0.20 m layer only treatments with C

  11. Pore size distribution analysis of activated carbons prepared from coconut shell using methane adsorption data

    NASA Astrophysics Data System (ADS)

    Ahmadpour, A.; Okhovat, A.; Darabi Mahboub, M. J.

    2013-06-01

    The application of Stoeckli theory to determine pore size distribution (PSD) of activated carbons using high pressure methane adsorption data is explored. Coconut shell was used as a raw material for the preparation of 16 different activated carbon samples. Four samples with higher methane adsorption were selected and nitrogen adsorption on these adsorbents was also investigated. Some differences are found between the PSD obtained from the analysis of nitrogen adsorption isotherms and their PSD resulting from the same analysis using methane adsorption data. It is suggested that these differences may arise from the specific interactions between nitrogen molecules and activated carbon surfaces; therefore caution is required in the interpretation of PSD obtained from the nitrogen isotherm data.

  12. Effect of mica content on pore-size distribution and porosity of sandy sediment using proton nuclear magnetic resonance measurement

    NASA Astrophysics Data System (ADS)

    Kimura, S.

    2015-12-01

    As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study on effect of mica content on pore size distribution and porosity of sandy sediment. This study used proton nuclear magnetic resonance (NMR) to measure the pore-size distribution and porosity of specimen to investigate mica content effect in sandy sediment. A mixture of silica sand No. 7 and mica (mica of 0 wt. %, 5 wt. % and 20 wt. %) was used in this study. The median D50 by laser diffraction method was obtained as 215.7 μm of silica sand No. 7 and 278.9 μm of mica. Pore-size distributions of specimens by the distribution of transverse magnetic relaxation time (T2) measurement by NMR were performed for the water-saturated sample under effective confining pressure of 1.0 MPa. The peaks of pore-size distribution curves decreased and showed finer shifts with increasing of mica content. The porosity of silica sand No. 7 specimen was 46.3%, and that of mica 5% and 20 % were 45.9% and 42.2%m, respectively. A change in pore-size distribution and porosity were observed with an increasing ratio of mica.

  13. Application of SAXS and SANS in evaluation of porosity, pore size distribution and surface area of coal

    USGS Publications Warehouse

    Radlinski, A.P.; Mastalerz, Maria; Hinde, A.L.; Hainbuchner, M.; Rauch, H.; Baron, M.; Lin, J.S.; Fan, L.; Thiyagarajan, P.

    2004-01-01

    This paper discusses the applicability of small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) techniques for determining the porosity, pore size distribution and internal specific surface area in coals. The method is noninvasive, fast, inexpensive and does not require complex sample preparation. It uses coal grains of about 0.8 mm size mounted in standard pellets as used for petrographic studies. Assuming spherical pore geometry, the scattering data are converted into the pore size distribution in the size range 1 nm (10 A??) to 20 ??m (200,000 A??) in diameter, accounting for both open and closed pores. FTIR as well as SAXS and SANS data for seven samples of oriented whole coals and corresponding pellets with vitrinite reflectance (Ro) values in the range 0.55% to 5.15% are presented and analyzed. Our results demonstrate that pellets adequately represent the average microstructure of coal samples. The scattering data have been used to calculate the maximum surface area available for methane adsorption. Total porosity as percentage of sample volume is calculated and compared with worldwide trends. By demonstrating the applicability of SAXS and SANS techniques to determine the porosity, pore size distribution and surface area in coals, we provide a new and efficient tool, which can be used for any type of coal sample, from a thin slice to a representative sample of a thick seam. ?? 2004 Elsevier B.V. All rights reserved.

  14. Statistical physics studies of multilayer adsorption isotherm in food materials and pore size distribution

    NASA Astrophysics Data System (ADS)

    Aouaini, F.; Knani, S.; Ben Yahia, M.; Ben Lamine, A.

    2015-08-01

    Water sorption isotherms of foodstuffs are very important in different areas of food science engineering such as for design, modeling and optimization of many processes. The equilibrium moisture content is an important parameter in models used to predict changes in the moisture content of a product during storage. A formulation of multilayer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics. Some physicochemical parameters related to the adsorption process were introduced in the analytical model expression. The data tabulated in literature of water adsorption at different temperatures on: chickpea seeds, lentil seeds, potato and on green peppers were described applying the most popular models applied in food science. We also extend the study to the newest proposed model. It is concluded that among studied models the proposed model seems to be the best for description of data in the whole range of relative humidity. By using our model, we were able to determine the thermodynamic functions. The measurement of desorption isotherms, in particular a gas over a solid porous, allows access to the distribution of pore size PSD.

  15. In-situ method for determining pore size distribution, capillary pressure and permeability

    SciTech Connect

    Vinegar, H.J.; Waxman, M.H.

    1987-02-17

    A method is described for determining the pore sizes entered by the oil phase in an oil-bearing formation, comprising: logging the formation of interest with an induced polarization logging tool having at least one source electrode; computing from the induced polarization measurements obtained by the logging tool a normalized induced polarization response function; obtaining core material from the formation of interest; extracting the water and hydrocarbons from the core material; resaturating the core material with formation brine; measuring the normalized induced polarization response function for the core material; and determining the pore sizes containing oil in the formation by comparing the normalized induced polarization response function from the formation with the normalized induced polarization response function of the core.

  16. Impact of Matric Potential and Pore Size Distribution on Growth Dynamics of Filamentous and Non-Filamentous Soil Bacteria

    PubMed Central

    Wolf, Alexandra B.; Vos, Michiel; de Boer, Wietse; Kowalchuk, George A.

    2013-01-01

    The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data, combined with information on bacterial motility (expansion potential) across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities. PMID:24391805

  17. Impact of matric potential and pore size distribution on growth dynamics of filamentous and non-filamentous soil bacteria.

    PubMed

    Wolf, Alexandra B; Vos, Michiel; de Boer, Wietse; Kowalchuk, George A

    2013-01-01

    The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data, combined with information on bacterial motility (expansion potential) across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities. PMID:24391805

  18. Measuring location, size, distribution, and loading of NiO crystallites in individual SBA-15 pores by electron tomography.

    PubMed

    Friedrich, Heiner; Sietsma, Jelle R A; de Jongh, Petra E; Verkleij, Arie J; de Jong, Krijn P

    2007-08-22

    By the combination of electron tomography with image segmentation, the properties of 299 NiO crystallites contained in 6 SBA-15 pores were studied. A statistical analysis of the particle size showed that crystallites between 2 and 6 nm were present with a distribution maximum at 3 and 4 nm, for the number-weighted and volume-weighted curves, respectively. Interparticle distances between nearest neighbors were 1-3 nm with very few isolated crystallites. In the examined pores, a local loading twice the applied average of 24 wt % NiO was found. This suggests that a very high local loading combined with a high dispersion is achievable. PMID:17655305

  19. Determination of pore size distributions in capillary-channeled polymer fiber stationary phases by inverse size-exclusion chromatography and implications for fast protein separations.

    PubMed

    Wang, Zhengxin; Marcus, R Kenneth

    2014-07-18

    Capillary-channeled polymer (C-CP) fibers have been utilized as liquid chromatography stationary phases, primarily for biomacromolecule separations on the analytical and preparative scales. The collinear packing of the eight-channeled C-CP fibers provides for very efficient flow, allowing operation at high linear velocity (u>100mm s(-1)) and low backpressure (<2000psi) in analytical-scale separations. To take advantage of these fluid transport properties, there must not be mass transfer limitations as would be imposed by having an appreciably porous phase, wherein solute diffusion limits the overall mass transport rates. To better understand the physical nano-/micro- structure of C-CP fibers, inverse size exclusion chromatography (iSEC) has been employed to determine the pore size distribution (PSD) within C-CP fibers. A diversity of test species (from metal ions to large proteins) was used as probes under non-retaining conditions to obtain a response curve reflecting the apparent partition coefficient (Kd) versus hydrodynamic radii (rm). A mean pore radius (rp) of 4.2nm with standard deviation (sp) of ±1.1nm was calculated by fitting the Kd versus rm data to model equations with a Gaussian pore size distribution, and a pore radius of 4.0±0.1nm was calculated based on a log-normal distribution. The derived mean pore radius is much smaller than traditional support materials, with the standard deviation showing a relatively uniform pore distribution. van Deemter plots were analyzed to provide practical confirmation of the structural implications. Large molecules (e.g., proteins) that are fully excluded from pores have no significant C-terms in the van Deemter plots whereas small molecules that can access the pore volumes display appreciable C-terms, as expected. Fitting of retention data to the Knox equation suggests that the columns operate with a characteristic particle diameter (dp) of ∼53μm. PMID:24877979

  20. Pore size distributions in uranium dioxide and uranium dioxide-gadolinium oxide fuel kernel produced by sol-gel technique

    NASA Astrophysics Data System (ADS)

    Gündüz, Güngör; Önal, Işik; Durmazuçar, Hasan H.

    1991-02-01

    Small kernels of UO 2-Gd 2O 3 were produced from their nitrate solutions by the application of sol-gel process in place of the more conventional process of mixing powders. The sol-gel method consisted of the following steps: sol preparation, sol drop dispersion, gellation, washing of gelled microspheres, aging, drying, calcination, reduction, and sintering. The effect of reduction temperature (873, 1073 and 1773 K) under a reducing gas mixture of 50% H2 + 50% N2 on pore volume and pore size distribution, was studied both for UO 2 and UO 2-Gd 2O 3 containing microspheres. The results indicated decreasing pore volume with increasing temperature as expected. However, the incorporation of Gd 2O 3 into UO 2 in the sol had a retardation effect in sintering which resulted in higher pore volume than that of UO 2-only microspheres. Mean pore diameter also remained small (about 950 nm) for UO 2-Gd 2O 3 samples after reduction (sintering at 1773 K) when compared to 1400 nm for UO 2-only samples. X-ray diffraction studies showed uniform distribution of Gd 2O 3 with no phase separation as well as a decrease in lattice parameter of UO 2 indicating incorporation of Gd 2O 3 into UO 2 lattice structure.

  1. Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

    NASA Astrophysics Data System (ADS)

    Zuliani, Jocelyn E.; Tong, Shitang; Kirk, Donald W.; Jia, Charles Q.

    2015-12-01

    Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

  2. Transport and Aggregation of Nanoparticles in Packed Beds: Effects of Pore Velocity and Initially-Fed Particle Size on Transient Particle Size Distributions

    NASA Astrophysics Data System (ADS)

    Pham, Ngoc; Papavassiliou, Dimitrios

    2015-11-01

    Aggregation of colloidal particles in flow through porous media has received careful consideration, as it reduces particle breakthrough due to pore clogging and sedimentation. Additionally, in unstable colloidal systems, deposition of colloidal aggregates on the pore surfaces can create sub-surfaces for further colloidal attachment. This phenomenon is known as ripening effect. In this study, transient particle size distributions of nano-particle systems, propagating in a bed packed with spheres are numerically investigated. In our simulation, only pair interactions are considered, and the aggregation rate is varied with the relative position of two particles in a pair. The packed bed consists of spheres of known size, randomly packed in a simulation box. To generate the velocity field of water inside the porous medium, the lattice Boltzmann method (LBM) is used. In conjunction with that, the trajectories of thousands of massless particles moving with the flow under convection and diffusion are recorded employing a Lagrangian framework. While pore clogging is neglected, we draw attention to the change of the distribution of particle size under different pore velocities and different initially-fed particle sizes.

  3. The role of beaded activated carbon's pore size distribution on heel formation during cyclic adsorption/desorption of organic vapors.

    PubMed

    Jahandar Lashaki, Masoud; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

    2016-09-01

    The effect of activated carbon's pore size distribution (PSD) on heel formation during adsorption of organic vapors was investigated. Five commercially available beaded activated carbons (BAC) with varying PSDs (30-88% microporous) were investigated. Virgin samples had similar elemental compositions but different PSDs, which allowed for isolating the contribution of carbon's microporosity to heel formation. Heel formation was linearly correlated (R(2)=0.91) with BAC micropore volume; heel for the BAC with the lowest micropore volume was 20% lower than the BAC with the highest micropore volume. Meanwhile, first cycle adsorption capacities and breakthrough times correlated linearly (R(2)=0.87 and 0.93, respectively) with BAC total pore volume. Micropore volume reduction for all BACs confirmed that heel accumulation takes place in the highest energy pores. Overall, these results show that a greater portion of adsorbed species are converted into heel on highly microporous adsorbents due to higher share of high energy adsorption sites in their structure. This differs from mesoporous adsorbents (low microporosity) in which large pores contribute to adsorption but not to heel formation, resulting in longer adsorbent lifetime. Thus, activated carbon with high adsorption capacity and high mesopore fraction is particularly desirable for organic vapor application involving extended adsorption/regeneration cycling. PMID:27173087

  4. Influence of pore size distributions on decomposition of maize leaf residue: evidence from X-ray computed micro-tomography

    NASA Astrophysics Data System (ADS)

    Negassa, Wakene; Guber, Andrey; Kravchenko, Alexandra; Rivers, Mark

    2014-05-01

    Soil's potential to sequester carbon (C) depends not only on quality and quantity of organic inputs to soil but also on the residence time of the applied organic inputs within the soil. Soil pore structure is one of the main factors that influence residence time of soil organic matter by controlling gas exchange, soil moisture and microbial activities, thereby soil C sequestration capacity. Previous attempts to investigate the fate of organic inputs added to soil did not allow examining their decomposition in situ; the drawback that can now be remediated by application of X-ray computed micro-tomography (µ-CT). The non-destructive and non-invasive nature of µ-CT gives an opportunity to investigate the effect of soil pore size distributions on decomposition of plant residues at a new quantitative level. The objective of this study is to examine the influence of pore size distributions on the decomposition of plant residue added to soil. Samples with contrasting pore size distributions were created using aggregate fractions of five different sizes (<0.05, 0.05-0.1, 0.10-05, 0.5-1.0 and 1.0-2.0 mm). Weighted average pore diameters ranged from 10 µm (<0.05 mm fraction) to 104 µm (1-2 mm fraction), while maximum pore diameter were in a range from 29 µm (<0.05 mm fraction) to 568 µm (1-2 mm fraction) in the created soil samples. Dried pieces of maize leaves 2.5 mg in size (equivalent to 1.71 mg C g-1 soil) were added to half of the studied samples. Samples with and without maize leaves were incubated for 120 days. CO2 emission from the samples was measured at regular time intervals. In order to ensure that the observed differences are due to differences in pore structure and not due to differences in inherent properties of the studied aggregate fractions, we repeated the whole experiment using soil from the same aggregate size fractions but ground to <0.05 mm size. Five to six replicated samples were used for intact and ground samples of all sizes with and without

  5. Solute Diffusivity of Repacked Volcanic Ash Soil: Effect of Changes in Pore Size Distribution due to Soil Compaction

    NASA Astrophysics Data System (ADS)

    Perera, M. S.; Resurreccion, A. C.; Kawamoto, K.; Komatsu, T.; Moldrup, P.

    2007-12-01

    Diffusion is the dominant spreading mechanism of contaminants dissolved in soil-water in the absence of soil- water flow. Solute diffusion coefficient, Ds, is a key parameter in investigating the fate and transport of contaminants from a polluted soil site. However, only a few studies on quantifying Ds as a function of soil- water content were done, especially for aggregated soils with a dual pore system such as volcanic ash soils (Andisols). In this study, we investigated the effect of bulk density on pore size distribution, and, consequently, on solute diffusivity (Ds/Do, where Do is the solute diffusion coefficient in pure water) in repacked volcanic ash soil taken at 5-10 cm depth at a pasture site in Nishi-Tokyo, Japan. Measurements of Ds were done on sieved and repacked soil at three bulk densities (0.62 g cm-3 , 0.7 g cm-3, and 0.8 g cm-3 ) and at three soil moisture conditions at pF (= log (-ψ; soil-water matric potential in cm H2O)) 1.8, 2, and 3 for each bulk density. Half-cell method was used to measure Ds where the source and sink half cells (each cell of 10-cm length and 4.9 cm in diameter) were joined together and the concentration profile was analyzed after a substantial time to determine Ds. Results showed that at a particular bulk density, Ds decreased with decreasing degree of saturation. This is expected since as the soil becomes drier, water films become disconnected resulting in a decrease in Ds. On the other hand, at a particular degree of saturation, the magnitude of Ds considerably decreases with increasing dry bulk density. As soil is compacted (and thus the increase in bulk density), the observed pore size distribution obtained from soil-water retention curve changes where the mainly inter-aggregate large pores become smaller and soil particles become closer to each other. This reduction in inter-aggregate pore size likely increases the liquid-phase tortuosity resulting in the decrease in Ds/Do at soil-water content at pF < 3. The soil

  6. Control of pore size in epoxy systems.

    SciTech Connect

    Sawyer, Patricia Sue; Lenhart, Joseph Ludlow; Lee, Elizabeth; Kallam, Alekhya; Majumdar, Partha; Dirk, Shawn M.; Gubbins, Nathan; Chisholm, Bret J.; Celina, Mathias Christopher; Bahr, James; Klein, Robert J.

    2009-01-01

    Both conventional and combinatorial approaches were used to study the pore formation process in epoxy based polymer systems. Sandia National Laboratories conducted the initial work and collaborated with North Dakota State University (NDSU) using a combinatorial research approach to produce a library of novel monomers and crosslinkers capable of forming porous polymers. The library was screened to determine the physical factors that control porosity, such as porogen loading, polymer-porogen interactions, and polymer crosslink density. We have identified the physical and chemical factors that control the average porosity, pore size, and pore size distribution within epoxy based systems.

  7. Multi-scale analysis in carbonates by X-ray microtomography: Characterization of the porosity and pore size distribution

    NASA Astrophysics Data System (ADS)

    Fernandes, Jaquiel S.; Nagata, Rodrigo; Moreira, Anderson C.; Fernandes, Celso P.; Appoloni, Carlos R.

    2013-05-01

    The porous systems of reservoir rocks present a complex geometry, involving aspects of shape of pores (morphology) and connectivity between the pores (topology). The macroscopic physical properties of these materials are strongly dependent of their microstructures. Based on these aspects, the present study has as main objective the characterization of the porous system geometry and computational determination of petrophysics properties of carbonate reservoir rocks through the X-ray microtomography methodology. Samples were microtomographed with the microtomographs Skyscan model 1172, installed at the PETROBRAS Research and Development Center (CENPES), Rio de Janeiro-RJ, Brazil and model 1173, installed at Sedimentary Geology Laboratory (LAGESD) in the Federal University of Rio de Janeiro (UFRJ). Two samples of carbonates were measured, Travertine and Dolomite, with spatial resolutions of 7 μm and 9.8 μm and 1.3 μm, 7 μm and 17 μm, respectively for the travertine and dolomite. With the data collected in the acquisitions, 900 transversal sections were reconstructed for each one of the referred resolutions. For the sample of dolomite, the average porosity found was 21.64%, 20.92% and 15.97% for resolutions of 1.3 μm, 7 μm and 17 μm, respectively. For the sample of travertine, the average porosity was 7.80 % and 7.52 % for resolutions of 7 μm and 9.8 μm, respectively. For the sample of dolomite, the pore size distribution showed that 50 % of the porous phase has pores with radius up to 37.6 μm, 84.6 μm and 84.4 μm, for the spatial resolutions of 1.3 μm, 7 μm and 17 μm, respectively. For the sample of travertine, 50 % of the pores have radius up to 148.1 μm and 158.1 μm, for the spatial resolutions of 7 μm and 9.8 μm.

  8. Non-linear behaviour of electrical parameters in porous, water-saturated rocks: a model to predict pore size distribution

    NASA Astrophysics Data System (ADS)

    Hallbauer-Zadorozhnaya, Valeriya; Santarato, Giovanni; Abu Zeid, Nasser

    2015-08-01

    In this paper, two separate but related goals are tackled. The first one is to demonstrate that in some saturated rock textures the non-linear behaviour of induced polarization (IP) and the violation of Ohm's law not only are real phenomena, but they can also be satisfactorily predicted by a suitable physical-mathematical model, which is our second goal. This model is based on Fick's second law. As the model links the specific dependence of resistivity and chargeability of a laboratory sample to the injected current and this in turn to its pore size distribution, it is able to predict pore size distribution from laboratory measurements, in good agreement with mercury injection capillary pressure test results. This fact opens up the possibility for hydrogeophysical applications on a macro scale. Mathematical modelling shows that the chargeability acquired in the field under normal conditions, that is at low current, will always be very small and approximately proportional to the applied current. A suitable field test site for demonstrating the possible reliance of both resistivity and chargeability on current was selected and a specific measuring strategy was established. Two data sets were acquired using different injected current strengths, while keeping the charging time constant. Observed variations of resistivity and chargeability are in agreement with those predicted by the mathematical model. These field test data should however be considered preliminary. If confirmed by further evidence, these facts may lead to changing the procedure of acquiring field measurements in future, and perhaps may encourage the design and building of a new specific geo-resistivity meter. This paper also shows that the well-known Marshall and Madden's equations based on Fick's law cannot be solved without specific boundary conditions.

  9. A general model for nonwetting phase relative permeability of disturbed porous media with lognormal pore size distribution

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Mohanty, B.

    2013-12-01

    Describing convective nonwetting phase flow in unsaturated porous media requires knowledge of relative nonwetting pahse permeability. This study was mainly conducted to formulate a general nonwetting pahse relative permeability model for porous media with lognormal pore size distribution based on Kosugi (1999) work for unsaturated relative hydraulic conductivity. The model-data comparison showed that the existing commonly used Burdine and Mualem permeability model could overestimate experimental relative nonwetting phase permeability data. The sensitivity analysis of the permeability model emphasized the importance of different pore tortuosity-connectivity value for gas and water phase. Subsequently, the suggested modified Burdine and Mualem permeability model for (alpha,beta,eta) in the general nonwetting phase permeability model should be (2.5, 2, 1) and (2, 1, 2) respectively. These two suggested models have the lowest mean root mean square error (RMSE) among the investigated permeability models. This finding could present more accurate permeability model parameterization in the multiphase subsurface flow modeling under isothermal and non-isothermal conditions.

  10. Pore size distribution of soil near saturation as affected by soil type, land use, and soil amendments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Storage and flow of water in soil voids, which are related to the size and geometry of the voids and flow rate are usually controlled by the void of the smallest size. Another reason for the complexity of water flow in soils is the intricate nature and change of the soil pores due to the modificatio...

  11. Effect of rock composition and texture on pore size distributions in shales: Applications in low field nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Saidian, Milad

    There are various methods to assess the pore size distribution (PSD) of porous materials; amongst all, NMR is the only technique that can be utilized for subsurface applications. The key parameter to transform NMR time domain response to PSD size domain data is surface relaxivity. The common practice is to consider a constant surface relaxivity throughout a well, formation or rock type regardless of the variations in rock compositions; this results in inaccurate PSD estimation using NMR log data. In this thesis I established a methodology to calculate the surface relaxivity in shales considering the rock composition and texture. I present the steps to achieve this goal in three steps: (a) Understanding the challenges of NMR acquisition, analysis and interpretation in shales, (b) Measuring the porosity, PSD and surface area and providing a practice to check the reliability of these measurements in shales, (c) Developing a methodology to calculate the surface relaxivity honoring the variations paramagnetic mineral content, susceptibility, distribution and texture. Application of NMR in unconventional rocks requires adjustment of NMR data acquisition and analysis to the unique properties of these rocks such as high level of heterogeneity, complex pore structure, fine grains, and presence of nano-scale pores. Identifying these challenges improves our understanding of NMR response in shales and increases the quality of the acquired and analyzed data. Calculation of surface relaxivity, as a measure of how fluids and rock surfaces react, requires reliable measurement of different petrophysical properties of the rock such as porosity, total specific surface area, and PSD using other techniques. I studied the reliability of different techniques to measure these petrophysical properties for shales by performing a thorough comparative study of porosity and PSD for different shale formations. The result of my study showed that clay type and content, total organic carbon (TOC

  12. Nonlinear Effect of Moisture Content on Effective Thermal Conductivity of Building Materials with Different Pore Size Distributions

    NASA Astrophysics Data System (ADS)

    Liu, Yanfeng; Ma, Chao; Wang, Dengjia; Wang, Yingying; Liu, Jiaping

    2016-06-01

    Understanding the quantitative relationship between the effective thermal conductivity and the moisture content of a material is required to accurately calculate the envelope heat and mass transfer and, subsequently, the building energy consumption. We experimentally analyzed the pore size distributions and porosities of common building materials and the influence of the moisture content on the effective thermal conductivity of building materials. We determined the quantitative relationship between the effective thermal conductivity and moisture content of building materials. The results showed that a larger porosity led to a more significant effect of the moisture content on the effective thermal conductivity. When the volumetric moisture content reached 10 %, the thermal conductivities of foam concrete and aerated concrete increased by approximately 200 % and 100 %, respectively. The effective thermal conductivity increased rapidly in the low moisture content range and increased slowly in the high moisture content range. The effective thermal conductivity is related to the moisture content of the materials through an approximate power function. As the moisture content in the walls of a new building stabilizes, the effective thermal conductivity of normal concrete varies only slightly, whereas that of aerated concrete varies more significantly. The effective thermal conductivity of the material is proportional to the relative humidity of the environment. This trend is most noticeable when the wall material is aerated concrete.

  13. Size of seismic events during borehole injections: the effects of source mechanisms, stress and pore pressure distribution

    NASA Astrophysics Data System (ADS)

    Fischer, T.; Ondovcin, T.; Zhao, P.

    2012-12-01

    and space-time distributions, source mechanisms and stress analyses on the available data to shed light on these questions. Our inversion for moment tensors of the Basel injection-induced seismicity shows that the microearthquakes had higher non-DC components during injection than after shut-in. This could be related to the higher stress drops found during injection. We model the pore pressure distribution and out-flow from the well the numerically solving the diffusion equation for the shut-in and open-well conditions. We compare the results of seismicity analysis with the models of pore pressure distribution during and after the injection to test the relevancy of several hypotheses of the occurrence of large events. We find that their anomalous occurrence during the shut-in phase is most-likely caused by the transient effects during the stop of injection. The anomalous space occurrence of large events is probably also related to the unequal distribution of faults in the vicinity of the injection well.

  14. Deriving NMR surface relaxivities, pore size distributions and water retention curves by NMR relaxation experiments on partially de-saturated rocks

    NASA Astrophysics Data System (ADS)

    Mohnke, O.; Nordlund, C. L.; Klitzsch, N.

    2013-12-01

    Nuclear magnetic resonance (NMR) is a method used over a wide field of geophysical applications to non-destructively determine transport and storage properties of rocks and soils. In NMR relaxometry signal amplitudes correspond directly to the rock's fluid (water, oil) content. On the other hand the NMR relaxation behavior, i.e. the longitudinal (T1) and transverse (T2) NMR relaxation times, can be used to derive pore sizes and permeability as it is linearly linked to the pore's surface-to-volume-ratio and physiochemical properties of the rock-fluid interface by the surface relaxivity ρ_s This parameter, however, is dependent on the type and mineral constituents of the investigated rock sample and thus has to be determined and calibrated prior to estimating pore sizes from NMR relaxometry measurements. Frequently used methods to derive surface relaxivity to calibrate NMR pore sizes comprise mercury injection, pulsed field gradients (PFG-NMR) or grain size analysis. This study introduces an alternative approach to jointly estimate NMR surface relaxivity and pore radii distributions using NMR relaxation data obtained from partially de-saturated rocks. In this, inverse modeling is carried on a linked Young Laplace equation for capillary bundles and the Brownstein and Tarr equations. Subsequently, this approach is used to predict water retention curves of the investigated rocks. The method was tested and validated on simulated and laboratory transverse NMR data. Calculated inverse models are generally in a good agreement with results obtained from mercury injection and drainage measurements. Left: Measured and predicted water retention (pF) curves. Center: NMR relaxometry data, fit and error. Right: Mercury injection data (HgPor, dashed line) and jointly derived pore radii distributions and surface relaxivity by joint inverse modelling

  15. Ovariectomized rats' femur treated with fibrates and statins. Assessment of pore-size distribution by ¹H-NMR relaxometry.

    PubMed

    Şipoş, Remus Sebastian; Fechete, Radu; Chelcea, Ramona Ioana; Moldovan, Dumitriţa; Pap, Zsuzsánna; Pávai, Zoltán; Demco, Dan Eugen

    2015-01-01

    The effects of two wonder drugs, simvastatins and fenofibrates on the proximal part of the femoris of a series of ovariectomized and non-ovariectomized Wistar albino rats was estimated qualitatively and semi-quantitatively by the modern method of 1D 1H-NMR T2-distribution. The 72 rats subjected to this study were divided in six groups and were sacrificed at two, four, six and eight weeks after ovariectomy and the proximal part of femoris was harvested. The CPMG (Carr-Purcell-Meiboom-Gill) echoes train curves were measured for the bones fully saturated with water during two months after two months of natural drying. These decays were analyzed by Laplace inversion and an average of normalized T2-distributions was considered for all rat's groups. The 1D averaged T2-distributions present four peaks, which were associated with protons in four major environments, from which the free water protons are used as spy molecules to explore the boundaries of cavities. In the approximation of spherical pores, the averaged T2-distributions were transformed in distributions of pores diameters. These were found in the range from 2 μm up to 2 mm. The relative amplitudes, widths and position of deconvoluted distributions of small, medium and large cavities are used for a qualitatively analysis of the effect of our lipid-lowering drugs. For a semi-quantitatively analysis, we chose the diameter d of proximal part of femoris' trabecular cavities. We show that the positive or negative effects of treatments with simvastatins and fenofibrates are strongly dependent on the duration of treatment. Moreover, the treatment of healthy bone is generally counter-indicated. PMID:26429167

  16. Pore size engineering applied to starved electrochemical cells and batteries

    NASA Technical Reports Server (NTRS)

    Abbey, K. M.; Thaller, L. H.

    1982-01-01

    To maximize performance in starved, multiplate cells, the cell design should rely on techniques which widen the volume tolerance characteristics. These involve engineering capillary pressure differences between the components of an electrochemical cell and using these forces to promote redistribution of electrolyte to the desired optimum values. This can be implemented in practice by prescribing pore size distributions for porous back-up plates, reservoirs, and electrodes. In addition, electrolyte volume management can be controlled by incorporating different pore size distributions into the separator. In a nickel/hydrogen cell, the separator must contain pores similar in size to the small pores of both the nickel and hydrogen electrodes in order to maintain an optimum conductive path for the electrolyte. The pore size distributions of all components should overlap in such a way as to prevent drying of the separator and/or flooding of the hydrogen electrode.

  17. Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa C.; Yohannes, Bereket; Hill, Kimberly M.; Dietrich, William E.

    2016-02-01

    Debris flows are typically a saturated mixture of poorly sorted particles and interstitial fluid, whose density and flow properties depend strongly on the presence of suspended fine sediment. Recent research suggests that grain size distribution (GSD) influences excess pore pressures (i.e., pressure in excess of predicted hydrostatic pressure), which in turn plays a governing role in debris flow behaviors. We report a series of controlled laboratory experiments in a 4 m diameter vertically rotating drum where the coarse particle size distribution and the content of fine particles were varied independently. We measured basal pore fluid pressures, pore fluid pressure profiles (using novel sensor probes), velocity profiles, and longitudinal profiles of the flow height. Excess pore fluid pressure was significant for mixtures with high fines fraction. Such flows exhibited lower values for their bulk flow resistance (as measured by surface slope of the flow), had damped fluctuations of normalized fluid pressure and normal stress, and had velocity profiles where the shear was concentrated at the base of the flow. These effects were most pronounced in flows with a wide coarse GSD distribution. Sustained excess fluid pressure occurred during flow and after cessation of motion. Various mechanisms may cause dilation and contraction of the flows, and we propose that the sustained excess fluid pressures during flow and once the flow has stopped may arise from hindered particle settling and yield strength of the fluid, resulting in transfer of particle weight to the fluid. Thus, debris flow behavior may be strongly influenced by sustained excess fluid pressures controlled by particle settling rates.

  18. The role of fine material and grain size distribution on excess pore pressure dissipation and particle support mechanisms in granular deposits based in large-scale physical experiments

    NASA Astrophysics Data System (ADS)

    Palucis, M. C.; Kaitna, R.; Tewoldebrhan, B.; Hill, K. M.; Dietrich, W. E.

    2011-12-01

    The dominant mechanisms behind sustained mobilization in granular debris flows are poorly understood, and experiments are needed to determine the conditions under which the fluid can fully support the coarse fraction. However, field-scale studies are difficult to instrument and constrain and laboratory studies suffer from scaling issues. A 4-m rotating drum located at UC Berkeley's Richmond Field Station allowed us to perform reproducible experiments with materials similar to those in the field to explore mechanisms relevant to slow pore fluid pressure dissipation. Specifically, we performed a series of experiments to assess the role of fines and grain size distribution on the rate of pore fluid pressure dissipation upon deposition of a granular mass. For each experiment we kept the total mass of the gravel particles constant and varied the amount of fines (from no fines to amounts found in an actual debris flow deposit) and the gravel particle size distribution (from a single grain size to a range found in natural flows). We first rotated each mixture in the drum, during which we monitored fluid pressures at the base of the flows (near the wall of the drum and at the center). Then we stopped the drum and continued to monitor the fluid pressures. Immediately upon stopping, the pore fluid pressure was nearly hydrostatic for the gravel-water flows, and any elevated pore pressure quickly dissipated. On the other hand, the mixtures with fines contents close to those found in actual debris flows had elevated pore pressures indicating they were almost fully liquefied. Furthermore, the rate of pore pressure dissipation was an order of magnitude slower than when no fines were present; the grain size distribution of the coarse fraction did not strongly influence the dissipation rates in either case. We also placed a cobble upon a fines-rich mixture after cessation of motion above the center pressure sensor, and observed that the pore fluid pressure rose instantly, bearing

  19. Effect of the pore size distribution on the activities of alumina supported Co-Mo catalysts in the hydrotreatment of boscan crude

    SciTech Connect

    Plumail, J.C.; Jacquin, Y.; Martino, G.; Toulhoat, H.

    1983-03-01

    The effects of pore size and distribution on the activity of Co-Mo/Al/sub 2/O/sub 3/ catalysts in the hydrotreatment of asphaltenes have been studied using testing methodology designed to provide initial activities for the catalysis of the critical reactions in the process, hydrodesulfurization (HDS), hydrodemineralization (HDM) (V,NI) and asphaltene conversion to resins and oils (HDA) suitable for subsequent use as refining feedstocks. Nine monomodal (micropores) and seven bimodal (micro- and macropores) were tested. Maximum HDS occurs with mono- and bimodal catalysts having an average pore diameter of 100 A/sup 0/. Maximum HDA and HDM activity appears at a pore diameter between 150 and 200 A/sup 0/ and increases with increasing macroporosity, macropores allowing more efficient access of the large asphaltene molecular units to active sites. Overall catalytic efficiency is dependent upon but HDS and asphaltene hydrogenation rates. Variation of pore structures allowed reaction selectivities to be varied and provided control a asphaltene product (resins, oils) composition.

  20. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N2 and CO2 adsorption isotherms? Simulation results for a realistic carbon model

    NASA Astrophysics Data System (ADS)

    Furmaniak, Sylwester; Terzyk, Artur P.; Gauden, Piotr A.; Harris, Peter J. F.; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N2 and CO2 isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO2, and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions.

  1. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N(2) and CO(2) adsorption isotherms? Simulation results for a realistic carbon model.

    PubMed

    Furmaniak, Sylwester; Terzyk, Artur P; Gauden, Piotr A; Harris, Peter J F; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N(2) and CO(2) isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO(2), and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions. PMID:21828590

  2. Metal oxide porous ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1991-01-01

    A method is disclosed for the production of metal oxide ceramic membranes of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  3. Metal oxide porous ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1992-01-01

    A method is disclosed for the production of metal oxide ceramic membranes of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  4. Pore size analysis of activated carbons from argon and nitrogen porosimetry using density functional theory

    SciTech Connect

    Dombrowski, R.J.; Hyduke, D.R.; Lastoskie, C.M.

    2000-05-30

    The authors present isotherms calculated from density functional theory for the adsorption of argon in model slit-shaped carbon pores at 77 K. The model isotherms are used to interpret experimental argon uptake measurements and to obtain the pore size distributions of several porous carbons. A similar set of density measurements and to obtain the pore size distributions of several porous carbons. A similar set of density functional theory isotherms, previously reported for nitrogen adsorption on carbon slit pores at 77 K, are used to determine pore size distributions for the same set of carbons. The pore size distribution maxima, mean pore widths, and specific pore volumes measured using the two different probe gases are all found to agree to within approximately 8% on average. Some of the differences in the pore size distributions obtained from argon and nitrogen porosimetry may be attributable to quadrupolar interactions of the nitrogen molecules with functional groups on the carbon surface.

  5. Effect of seawater salinity on pore-size distribution on a poly(styrene)-based HP20 resin and its adsorption of diarrhetic shellfish toxins.

    PubMed

    Fan, Lin; Sun, Geng; Qiu, Jiangbing; Ma, Qimin; Hess, Philipp; Li, Aifeng

    2014-12-19

    In the present study, okadaic acid (OA) and dinophysistoxin-1 (DTX1) were spiked into artificial seawater at low, medium and high estuarine salinities (9‰, 13.5‰ and 27‰). Passive samplers (HP20 resin) used for solid phase adsorption toxin tracking (SPATT) technology were exposed in these seawaters for 12-h periods. Adsorption curves well fitted a pseudo-secondary kinetics model. The highest initial sorption rates of both toxins occurred in the seawater of medium salinity, followed by seawater of low and high estuarine salinity. Pore volumes of micropores (<2 nm) and small mesopores (2 nmsize) in seawaters of high and low salinity. More toxin or other matrix agglomerates were displayed on the surface of resin deployed in the seawater of medium salinity. Taking into consideration the pore-size distribution and surface images, it appears that intra-particle diffusion governs toxin adsorption in seawater at high salinity while film diffusion mainly controls the adsorption process in seawater at medium salinity. This is the first study to confirm that molecules of OA and DTX1 are able to enter into micropores (<2nm) and small mesopores (2-10nm) of HP20 resin in estuarine seawater with high salinity (∼27‰). PMID:25464996

  6. Nano-pore size and porosity study by means of Nuclear Magnetic Resonance and Positronium Annihilation Lifetime

    NASA Astrophysics Data System (ADS)

    Chesta, M. A.; Ramia, M. E.; Jeandrevin, S.; Martín, C. A.

    2009-11-01

    The present work involves a comprehensive experimental determination of porosity and pore size distribution in rocks from oil fields formations by deuterium (2H) Nuclear Magnetic Resonance (NMR) and Positronium Annihilation Lifetime Spectroscopy (PALS). Both techniques yield complementary results; PALS measures the average pore size providing bulk information from which the most abundant pore size can be obtained, and NMR allows for the determination of the relative pore size distribution accurately. Both techniques give complementary information to obtain an absolute pore size distribution.

  7. Pore-size ion-size correlations for carbon supercapacitors

    NASA Astrophysics Data System (ADS)

    Chmiola, John

    2009-08-01

    Carbon supercapacitors, which are energy storage devices that use ion adsorption on the surface of highly porous materials to store charge, have numerous advantages over other power-source technologies, but could realize further gains if their electrodes were properly optimized. This could lead to fleet-wide improvements in economy, performance, lifetime and environmental impact of Hybrid Electric Vehicles (HEVs), as well as enable or advance many other applications. To determine correlations between ion-size and pore-size in carbon supercapacitors, we generated a well-characterized set of porous carbide-derived carbons (CDC) with average pore sizes from 0.6 to 2.25 nm and used them to probe the limits of understanding. Performing the first systematic study of the effect of pore size on capacitance showed that, in general, decreasing the pore size below the size of the solvated ion, or to precisely the size of the ionic liquid ion, allowed higher accumulation of charge. Using CDC with properly tuned porosity showed excellent performance in H2SO 4, ˜200 F/g, and performance superior to all prior reported results in organic (CH3CH2)4NBF4 (TEABF 4) electrolytes as well as l-ethyl-3-methyl immidazolium bis-(trifluoromethanesulfonyl)imide (EMI-TFSI) ionic liquid, ˜150 F/g. This work conclusively showed that precisely matching the pore size with the ion size is the key factor for maximizing capacitance. Understanding that pores significantly larger than the effective ion size do not have large contributions to energy storage, work on dense porous CDC films on conductive substrates showed ˜100% larger volumetric capacitance than any previously reported. Depositing patterned films of carbide and electrical contacts could lead to microfabricated energy storage devices directly on a chip, or built up in layers for performances yet unrealized.

  8. Pore size and the lab-field reaction rate riddle

    NASA Astrophysics Data System (ADS)

    Emmanuel, S.; Ague, J. J.; Walderhaug, O.

    2009-12-01

    Pore size is usually thought to influence the rate of crystal growth during diagenesis and metamorphism by controlling the ratio of surface area to fluid volume. However, theory suggests that in micron-scale to nanometer-scale pores, interfacial energy effects can also become important. We used mercury porosimetry to investigate the pore-size distributions in naturally cemented sandstone adjacent to stylolites and found that quartz precipitation was inhibited in pores smaller than 10 microns in diameter. We demonstrate that standard kinetic models cannot reproduce the observed pore-size patterns in mineralized samples; by contrast, excellent fits with the data are obtained when interfacial energy effects are taken into account. Moreover, as such micron-scale pores comprise the overwhelming majority of surface area in the sandstone, average reaction rates for the rock are significantly reduced. Reaction rates in geological media determined in field studies can be orders of magnitude lower than those measured in laboratory experiments, and we propose that reduced reaction rates in rocks with micron-scale porosity could account for the apparent paradox.

  9. Nanoporous carbide-derived carbons with tunable pore size

    NASA Astrophysics Data System (ADS)

    Fischer, John; Zhou, Wei; Gogotsi, Yury; Nikitin, Alexei; Ye, Haihui; Barsoum, Michel; Yi, Bo; Foley, Henry

    2004-03-01

    Major efforts in porous materials have been directed toward control of pore size, shape and uniformity. Here we demonstrate that porosity of carbide-derived carbons (CDCs) can be tuned with sub-Å accuracy in a wide range by controlling the chlorination temperature. CDCs have narrow pore size distributions, comparable to zeolites and much narrower than single-wall carbon nanotubes or activated carbons. Furthermore, mean pore diameters in the range 0.5 - 0.8 nm are obtained by dechlorination of Ti3SiC2 at temperatures from 300-1200 °C [1], suggesting possible application as a novel H2 storage material. Pore size distributions measured by Ar adsorption, Ch3Cl adsorption and small-angle x-ray scattering are in good agreement [1]. We introduce neutron prompt gamma activation analysis as a hydrogen-specific probe of storage capacity which can also be applied to in situ measurements of adsorption and desorption energies and kinetics. [1]. Y. Gogotsi, A. Nikitin, H. Ye, W. Zhou, J. E. Fischer, B. Ye, H. Foley and M. Barsoum, Nature Materials 2, 591(2003).

  10. Sulfur-infiltrated porous carbon microspheres with controllable multi-modal pore size distribution for high energy lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Cunyu; Liu, Lianjun; Zhao, Huilei; Krall, Andy; Wen, Zhenhai; Chen, Junhong; Hurley, Patrick; Jiang, Junwei; Li, Ying

    2013-12-01

    Sulfur has received increasing attention as a cathode material for lithium-sulfur (Li-S) batteries due to its high theoretical specific capacity. However, the commercialization of Li-S batteries is limited by the challenges of poor electrical conductivity of sulfur, dissolution of the polysulfide intermediates into the electrolyte, and volume expansion of sulfur during cycling. Herein, we report the fabrication of novel-structured porous carbon microspheres with a controllable multi-modal pore size distribution, i.e., a combination of interconnected micropores, mesopores and macropores. Cathodes made of sulfur infiltrated in such a hierarchical carbon framework provide several advantages: (1) a continuous and high surface area carbon network for enhanced electrical conductivity and high sulfur loading; (2) macropores and large mesopores bridged by small mesopores to provide good electrolyte accessibility and fast Li ion transport and to accommodate volume expansion of sulfur; and (3) small mesopores and micropores to improve carbon/sulfur interaction and to help trap polysulfides. An initial discharge capacity at 1278 mA h g-1 and capacity retention at 70.7% (904 mA h g-1) after 100 cycles at a high rate (1 C) were achieved. The material fabrication process is relatively simple and easily scalable.Sulfur has received increasing attention as a cathode material for lithium-sulfur (Li-S) batteries due to its high theoretical specific capacity. However, the commercialization of Li-S batteries is limited by the challenges of poor electrical conductivity of sulfur, dissolution of the polysulfide intermediates into the electrolyte, and volume expansion of sulfur during cycling. Herein, we report the fabrication of novel-structured porous carbon microspheres with a controllable multi-modal pore size distribution, i.e., a combination of interconnected micropores, mesopores and macropores. Cathodes made of sulfur infiltrated in such a hierarchical carbon framework provide

  11. Preparation of mesoporous cadmium sulfide nanoparticles with moderate pore size

    SciTech Connect

    Han Zhaohui Zhu, Huaiyong; Shi, Jeffrey; Parkinson, Gordon; Lu, G.Q.

    2007-03-15

    The preparation of cadmium sulfide nanoparticles that have a moderate pore size is reported. This preparation method involves a hydrothermal process that produces a precursor mixture and a following acid treatment of the precursor to get the porous material. The majority of the particles have a pore size close to 20nm, which complements and fills in the gap between the existing cadmium sulfide materials, which usually have a pore size either less than 10nm or are well above 100nm.

  12. Chemical potential and entropy in monodisperse and polydisperse hard-sphere fluids using Widom's particle insertion method and a pore size distribution-based insertion probability.

    PubMed

    Baranau, Vasili; Tallarek, Ulrich

    2016-06-01

    We estimate the excess chemical potential Δμ and excess entropy per particle Δs of computer-generated, monodisperse and polydisperse, frictionless hard-sphere fluids. For this purpose, we utilize the Widom particle insertion method, which for hard-sphere systems relates Δμ to the probability to successfully (without intersections) insert a particle into a system. This insertion probability is evaluated directly for each configuration of hard spheres by extrapolating to infinity the pore radii (nearest-surface) distribution and integrating its tail. The estimates of Δμ and Δs are compared to (and comply well with) predictions from the Boublík-Mansoori-Carnahan-Starling-Leland equation of state. For polydisperse spheres, we employ log-normal particle radii distributions with polydispersities δ = 0.1, 0.2, and 0.3. PMID:27276959

  13. Decreasing transmembrane segment length greatly decreases perfringolysin O pore size

    SciTech Connect

    Lin, Qingqing; Li, Huilin; Wang, Tong; London, Erwin

    2015-04-08

    Perfringolysin O (PFO) is a transmembrane (TM) β-barrel protein that inserts into mammalian cell membranes. Once inserted into membranes, PFO assembles into pore-forming oligomers containing 30–50 PFO monomers. These form a pore of up to 300 Å, far exceeding the size of most other proteinaceous pores. In this study, we found that altering PFO TM segment length can alter the size of PFO pores. A PFO mutant with lengthened TM segments oligomerized to a similar extent as wild-type PFO, and exhibited pore-forming activity and a pore size very similar to wild-type PFO as measured by electron microscopy and a leakage assay. In contrast, PFO with shortened TM segments exhibited a large reduction in pore-forming activity and pore size. This suggests that the interaction between TM segments can greatly affect the size of pores formed by TM β-barrel proteins. PFO may be a promising candidate for engineering pore size for various applications.

  14. Decreasing transmembrane segment length greatly decreases perfringolysin O pore size

    DOE PAGESBeta

    Lin, Qingqing; Li, Huilin; Wang, Tong; London, Erwin

    2015-04-08

    Perfringolysin O (PFO) is a transmembrane (TM) β-barrel protein that inserts into mammalian cell membranes. Once inserted into membranes, PFO assembles into pore-forming oligomers containing 30–50 PFO monomers. These form a pore of up to 300 Å, far exceeding the size of most other proteinaceous pores. In this study, we found that altering PFO TM segment length can alter the size of PFO pores. A PFO mutant with lengthened TM segments oligomerized to a similar extent as wild-type PFO, and exhibited pore-forming activity and a pore size very similar to wild-type PFO as measured by electron microscopy and a leakagemore » assay. In contrast, PFO with shortened TM segments exhibited a large reduction in pore-forming activity and pore size. This suggests that the interaction between TM segments can greatly affect the size of pores formed by TM β-barrel proteins. PFO may be a promising candidate for engineering pore size for various applications.« less

  15. Influence of Pore Size on Fracture Strength of Porous Ceramics

    NASA Astrophysics Data System (ADS)

    Yoshida, Keigo; Tsukidate, Hironori; Murakami, Akira; Miyata, Hiroshi

    Porous ceramics possess the excellent penetration and adiabatic characteristics, etc., and are used as heatproof filter materials for environmental equipments, etc. Moreover, porous ceramics controlled with porosity and pore size in the wide range have been actively developed. However, how the strength characteristics of porous ceramics are influenced by porosity and pore size of the material are not understood still enough. In this research, the evaluation tests on fracture strength, fracture energy and fracture toughness of porous alumina ceramics which porosity are almost equal, while pore sizes are different mutually were performed, and the relation between the pore size and the fracture strength was studied. The tests results show that the dispersion of fracture strength data is few though fracture strength of porous ceramics is lower than that of high-density ceramics. The relation based on linear fracture mechanics between the defect size and the fracture strength is valid when the one that a pore accompanies with the peculiar defect of the material was regarded as a defect size. In addition, fracture energy increases with the increase of pore size, and this seems based on a crooked propagation path of a crack. Finally, the process zone fracture model with considering the effect of the pore and grain size of the material is proposed. According to this model, for all pore size and crack length, it was shown that the fracture strengths of cracked specimens are evaluated.

  16. A framework for quantifying size dependent deformation of nano-scale pores in mudrocks

    NASA Astrophysics Data System (ADS)

    Emmanuel, Simon; Day-Stirrat, Ruarri J.

    2012-11-01

    The evolution of pore size distributions during sediment consolidation controls critical parameters such as porosity and permeability. Two phenomenological models are developed that describe the evolution of pore size distributions during stress induced consolidation. The first model predicts the evolution of pores subjected to an applied stress for systems in which all pores deform equally irrespective of size; in the second model, the rate of pore deformation decreases with size (i.e., smaller pores deform less readily than larger ones). To determine which model best describes the behavior of clay-rich rocks during consolidation, cumulative void volume curves from consolidation experiments carried out on Boston Blue Clay are compared with results from numerical simulations. While the uniform deformation model is able produce a good fit during the initial stage of the consolidation (0.1-1 MPa), it is unable to capture system behavior at elevated stresses (1-10 MPa). By contrast, the size dependent deformation model produces excellent fits with the data at both initial and later stages of consolidation. Furthermore, the model shows that size dependent behavior is restricted to pores with radii of < 100 nm; significantly, small pores may be up to 47% less compressible than large pores. Crucially, by comparing sediments from different burial depths but possessing similar mineralogical compositions, the framework can be used to assess the behavior of natural sediments under geological conditions.

  17. Construction of Nuclear Envelope Shape by a High-Genus Vesicle with Pore-Size Constraint.

    PubMed

    Noguchi, Hiroshi

    2016-08-23

    Nuclear pores have an approximately uniform distribution in the nuclear envelope of most living cells. Hence, the morphology of the nuclear envelope is a spherical stomatocyte with a high genus. We have investigated the morphology of high-genus vesicles under pore-size constraint using dynamically triangulated membrane simulations. Bending-energy minimization without volume or other constraints produces a circular-cage stomatocyte, where the pores are aligned in a circular line on an oblate bud. As the pore radius is reduced, the circular-pore alignment is more stabilized than a random pore distribution on a spherical bud. However, we have clarified the conditions for the formation of a spherical stomatocyte: a small perinuclear volume, osmotic pressure within nucleoplasm, and repulsion between the pores. When area-difference elasticity is taken into account, the formation of cylindrical or budded tubules from the stomatocyte and discoidal stomatocyte is found. PMID:27558725

  18. Anomalous cyclic voltammetric response from pores smaller than ion size by voltage-induced force.

    PubMed

    Yang, Cheol-Min; Jung, Hwan Jung; Kim, Yong Jung

    2015-05-15

    Nanoporous carbons, with different micropore size distributions, were prepared based on waste coffee grounds by a chemical activation process in order to elucidate the correlation between desolvated ions and pores smaller than the sizes of ions using an organic electrolyte. The pore structure of the coffee-based nanoporous carbon was strongly dependent on the heat-treatment temperature prior to the activation process. Cyclic voltammograms of the nanoporous carbons mainly dominated by the smaller pore relative to that of the bare ion size clearly showed deviation from an ideal feature of the current response. It was clearly envisaged that even a bare ion of a size larger than the pore size can penetrate into the pore by voltage-induced force. PMID:25668782

  19. Immobilization of nanobeads on a surface to control the size, shape and distribution of pores in electrochemically generated sol-gel films

    PubMed Central

    Ciabocco, Michela; Berrettoni, Mario; Zamponi, Silvia

    2015-01-01

    Electrochemically assisted deposition of an ormosil film at a potential where hydrogen ion is generated as the catalyst yields insulating films on electrodes. When the base electrode is modified with 20-nm poly(styrene sulfonate), PSS, beads bound to the surface with 3-aminopropyltriethoxysilane (APTES) and using (CH3)3SiOCH3 as the precursor, the resulting film of organically modified silica (ormosil) has cylindrical channels that reflect both the diameter of the PSS and the distribution of the APTES-PSS on the electrode. At an electrode modified by a 20-min immersion in 0.5 mmol dm-3 APTES followed by a 30-s immersion in PSS, a 20-min electrolysis at 1.5 V in acidified (CH3)3SiOCH3 resulted in an ormosil film with 20-nm pores separated by 100 nm. Cyclic voltammetry of Ru(CN)64- at scan rates above 5 mVs-1 yielded currents controlled primarily by linear diffusion. Below 5 mVs-1, convection rather than the expected factor, radial diffusion, apparently limited the current. PMID:26167128

  20. Size of diffusion pore of Alcaligenes faecalis.

    PubMed

    Ishii, J; Nakae, T

    1988-03-01

    The diffusion pore of the outer membrane of Alcaligenes faecalis was shown to be substantially smaller than the Escherichia coli porin pore. In experiments with intact cells, pentoses and hexoses penetrated into the NaCl-expanded periplasm, whereas saccharides of Mr greater than 342 did not. Cells treated with 0.5 M saccharides of Mr greater than 342 weighed 33 to 38% less than cells treated with isotonic solution, suggesting that these saccharides do not permeate through the outer membrane. The diffusion rates of various solutes through the liposome membranes reconstituted from the Mr-43,000 outer membrane protein showed the following characteristics. (i) The relative diffusion rates of pentoses, hexoses, and methylhexoses appeared to be about 1.0, 0.6, and negligibly small, respectively. (ii) The diffusion rate of glucose appeared to be about 1/10th that with the E. coli B porin. (iii) The diffusion rate of gluconic acid was five to seven times higher than that of glucose. (iv) The diffusion rates of beta-lactam antibiotics appeared to be 40 to less than 10% of those with the E. coli B porin. PMID:2835003

  1. Size of diffusion pore of Alcaligenes faecalis.

    PubMed Central

    Ishii, J; Nakae, T

    1988-01-01

    The diffusion pore of the outer membrane of Alcaligenes faecalis was shown to be substantially smaller than the Escherichia coli porin pore. In experiments with intact cells, pentoses and hexoses penetrated into the NaCl-expanded periplasm, whereas saccharides of Mr greater than 342 did not. Cells treated with 0.5 M saccharides of Mr greater than 342 weighed 33 to 38% less than cells treated with isotonic solution, suggesting that these saccharides do not permeate through the outer membrane. The diffusion rates of various solutes through the liposome membranes reconstituted from the Mr-43,000 outer membrane protein showed the following characteristics. (i) The relative diffusion rates of pentoses, hexoses, and methylhexoses appeared to be about 1.0, 0.6, and negligibly small, respectively. (ii) The diffusion rate of glucose appeared to be about 1/10th that with the E. coli B porin. (iii) The diffusion rate of gluconic acid was five to seven times higher than that of glucose. (iv) The diffusion rates of beta-lactam antibiotics appeared to be 40 to less than 10% of those with the E. coli B porin. Images PMID:2835003

  2. Laser damage dependence on the size and concentration of precursor defects in KDP crystals: view through differently sized filter pores.

    PubMed

    Wang, Yueliang; Zhao, Yuanan; Xie, Xiaoyi; Hu, Guohang; Yang, Liujiang; Xu, Ziyuan; Shao, Jianda

    2016-04-01

    We investigate the laser-induced damage performance at 1064 nm of potassium dihydrogen phosphate (KDP) crystals grown using filters of different pore sizes. The aim is to explore a novel method for understanding laser-matter interactions with regard to physical parameters affecting the ability of damage precursors to initiate damage. By reducing the pore size of filters in continuous filtration growth, we can improve laser damage resistance. Furthermore, we develop a model based on a Gaussian distribution of precursor thresholds and heat transfer to obtain a size distribution of the precursor defects. Smaller size and/or lower concentration of precursor defects could lead to better damage resistance. PMID:27192280

  3. Porous Boron Nitride with Tunable Pore Size.

    PubMed

    Dai, Jun; Wu, Xiaojun; Yang, Jinlong; Zeng, Xiao Cheng

    2014-01-16

    On the basis of a global structural search and first-principles calculations, we predict two types of porous boron-nitride (BN) networks that can be built up with zigzag BN nanoribbons (BNNRs). The BNNRs are either directly connected with puckered B (N) atoms at the edge (type I) or connected with sp(3)-bonded BN chains (type II). Besides mechanical stability, these materials are predicted to be thermally stable at 1000 K. The porous BN materials entail large surface areas, ranging from 2800 to 4800 m(2)/g. In particular, type-II BN material with relatively large pores is highly favorable for hydrogen storage because the computed hydrogen adsorption energy (-0.18 eV) is very close to the optimal adsorption energy (-0.15 eV) suggested for reversible hydrogen storage at room temperature. Moreover, the type-II materials are semiconductors with width-dependent direct bandgaps, rendering the type-II BN materials promising not only for hydrogen storage but also for optoelectronic and photonic applications. PMID:26270717

  4. EFFECT OF PORE SIZE ON TRAPPING ZINC VAPORS

    SciTech Connect

    Korinko, P.

    2010-12-17

    A series of experiments were conducted to determine the effect of pore size on pumping efficiency and zinc vapor trapping efficiency. A simple pumping efficiency test was conducted for all five pore diameters where it was observed that evacuation times were adversely affected by reducing the pore size below 5 {micro}m. Common test conditions for the zinc trapping efficiency experiments were used. These conditions resulted in some variability, to ascribe different efficiencies to the filter media. However, the data suggest that there is no significant difference in trapping efficiency for filter media with pores from 0.2 to 20 {micro}m with a thickness of 0.065-inch. Consequently, the 20 {micro}m pore filter media that is currently used at SRS is a suitable filter material for to utilize for future extractions. There is evidence that smaller pore filter will adversely affect the pumping times for the TEF and little evidence to suggest that a smaller pore diameters have significant impact on the trapping efficiency.

  5. Method of making metal oxide ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1992-01-01

    A method for the production of metal oxide ceramic membranes is composed of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  6. Distributed Pore Chemistry in Porous Organic Polymers

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    1998-01-01

    A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The sub-strate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphorylcholine groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge, wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic region, and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

  7. Distributed Pore Chemistry in Porous Organic Polymers

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    1999-01-01

    A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The substrate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphorylcholine groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge. wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic regions. and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

  8. Neutrons measure phase behavior in pores at Angstrom size

    SciTech Connect

    Bardoel, Agatha A; Melnichenko, Yuri B

    2012-01-01

    Researchers have measured the phase behavior of green house gases in pores at the Angstrom-level, using small angle neutron scattering (SANS) at the Oak Ridge National Laboratory's High Flux Isotope Reactor. Yuri Melnichenko, an instrument scientist on the General Purpose Small Angle Neutron Scattering (GP SANS) Diffractometer at ORNL's High Flux Isotope Reactor, his postdoctoral associate Lilin He and collaborators Nidia Gallego and Cristian Contescu from the Material Sciences Division (ORNL) were engaged in the work. They were studying nanoporous carbons to assess their attractiveness as storage media for hydrogen, with a view to potential use for on-board hydrogen storage for transportation applications. Nanoporous carbons can also serve as electrode material for supercapacitors and batteries. The researchers successfully determined that the most efficiently condensing pore size in a carbon nanoporous material for hydrogen storage is less than one nanometer. In a paper recently published by the Journal of the American Chemical Society, the collaborators used small angle neutron scattering to study how hydrogen condenses in small pores at ambient temperature. They discovered that the surface-molecule interactions create internal pressures in pores that may exceed the external gas pressure by a factor of up to 50. 'This is an exciting result,' Melnichenko said, 'as you achieve extreme densification in pores 'for free', i.e. without spending any energy. These results can be used to guide the development of new carbon adsorbents tailored to maximize hydrogen storage capacities.' Another important factor that defines the adsorption capacity of sub-nanometer pores is their shape. In order to get accurate structural information and maximize sorption capacity, it is important that pores are small and of approximately uniform size. In collaboration with Drexel University's Yury Gogotsi who supplied the samples, Melnichenko and his collaborators used the GP SANS

  9. Microfluidic production of porous carbon spheres with tunable size and pores.

    PubMed

    Ge, Han; Xu, Hongbao; Lu, Tianyi; Li, Jiang; Chen, Haosheng; Wan, Jiandi

    2016-01-01

    Porous carbon particles have been widely used in many areas including energy storage. Production of carbon microspheres in an efficient, controlled, and low-cost manner, however, is challenging. Here, we demonstrate a microfluidic approach to generate porous carbon particles using inexpensive precursors and show that the size of the particle and pores can be tuned by adjusting the deionized (DI) water content in droplets and preheating temperature. The developed strategy offers an effective approach to control the production of porous carbon spheres with a well-defined diameter, narrow size distribution and pore size. PMID:26397924

  10. Pore distributions in nanocrystalline metals from small-angle neutron scattering

    SciTech Connect

    Sanders, P.G.; Weertman, J.R.; Eastman, J.A.

    1998-07-24

    Recent upgrades in inert-gas condensation processing equipment have produced nanocrystalline metal samples with high densities and low-impurity levels. Typical Cu and Pd samples have densities {ge}98% of theoretical and oxygen and hydrogen impurity concentrations {le}0.5 at. %. Lower porosity and impurity levels may make it difficult to produce and maintain samples with the smallest nanocrystalline grain sizes. These improved samples were studied by small-angle neutron scattering (SANS) to determine the volume fraction and size distribution of pores. Excellent correlation was obtained between the total volume fraction of pores and the Archimedes density for Pd, signifying that most of the pores were relatively small and in the detectability range of SANS ({approx}1--100 nm). Nanocrystalline Cu is shown to exhibit a wider pore size distribution. For Pd, the average pore sizes were slightly smaller than the average grain size, while for Cu the pore size and grain size were about the same. Both materials exhibited a trend of increasing pore size with increasing grain size. In terms of processing prerequisites, the principal condition for the production of high-density nanocrystalline Cu is an exceptionally clean synthesis environment, while nanocrystalline Pd requires compaction at elevated temperatures. These differences are the result of Cu having both a lower melting point and a greater susceptibility to contamination by gaseous impurities such as oxygen.

  11. Anomalous or regular capacitance? The influence of pore size dispersity on double-layer formation

    NASA Astrophysics Data System (ADS)

    Jäckel, N.; Rodner, M.; Schreiber, A.; Jeongwook, J.; Zeiger, M.; Aslan, M.; Weingarth, D.; Presser, V.

    2016-09-01

    The energy storage mechanism of electric double-layer capacitors is governed by ion electrosorption at the electrode surface. This process requires high surface area electrodes, typically highly porous carbons. In common organic electrolytes, bare ion sizes are below one nanometer but they are larger when we consider their solvation shell. In contrast, ionic liquid electrolytes are free of solvent molecules, but cation-anion coordination requires special consideration. By matching pore size and ion size, two seemingly conflicting views have emerged: either an increase in specific capacitance with smaller pore size or a constant capacitance contribution of all micro- and mesopores. In our work, we revisit this issue by using a comprehensive set of electrochemical data and a pore size incremental analysis to identify the influence of certain ranges in the pore size distribution to the ion electrosorption capacity. We see a difference in solvation of ions in organic electrolytes depending on the applied voltage and a cation-anion interaction of ionic liquids in nanometer sized pores.

  12. Bovine Serum Albumin Adsorption in Mesoporous Titanium Dioxide: Pore Size and Pore Chemistry Effect.

    PubMed

    Liu, Chang; Guo, Yanhua; Hong, Qiliang; Rao, Chao; Zhang, Haijuan; Dong, Yihui; Huang, Liangliang; Lu, Xiaohua; Bao, Ningzhong

    2016-04-26

    Understanding the mechanism of protein adsorption and designing materials with high sensitivity, high specificity and fast response are critical to develop the next-generation biosensing and diagnostic platforms. Mesoporous materials with high surface area, tunable pores, and good thermal/hydrostatic stabilities are promising candidates in this field. Because of the excellent biocompatibility, titanium dioxide has received an increasing interest in the past decade for biomedical applications. In this work, we synthesized mesoporous titanium dioxide with controlled pore sizes (7.2-28.0 nm) and explored their application for bovine serum albumin (BSA) adsorption. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption/desorption experiments were performed to characterize the mesoporous TiO2 samples before and after BSA adsorption. Isothermal microcalorimetry was applied to measure both the adsorption heat and conformation rearrangement heat of BSA in those mesopores. We also carried out thermogravimetry measurements to qualitatively estimate the concentration of hydroxyl groups, which plays an important role in stabilizing BSA in-pore adsorption. The adsorption stability was also examined by leaching experiments. The results showed that TiO2 mesopores can host BSA adsorption when their diameters are larger than the hydrodynamic size of BSA (∼9.5 nm). In larger mesopores studied, two BSA molecules were adsorbed in the same pores. In contrast to the general understanding that large mesopores demonstrate poor stabilities for protein adsorptions, the synthesized mesoporous TiO2 samples demonstrated good leaching stabilities for BSA adsorption. This is probably due to the combination of the mesoporous confinement and the in-pore hydroxyl groups. PMID:27048991

  13. Optical transmission spectra of porous aluminamembranes with different pore size

    NASA Astrophysics Data System (ADS)

    Matyushkin, L. B.; Muratova, E. N.; Spivak, J. M.; Shimanova, V. V.; Korlyakova, S. A.; Moshnikov, V. A.

    2014-12-01

    Membranes of nanoporous aluminum oxide (alumina) have been obtained using the electrochemical etching technique by varying technological regimes. The surface morphology and cleavages of obtained experimental samples are studied using scanning electron microscopy (SEM). The optical transmission measurements were performed on a spectrophotometer in the wavelength range of 190-1000 nm. It is possible to determine the average size and the dispersion of the pore diameter by UV- visible transmittance spectrum measuring.

  14. Business size distributions

    NASA Astrophysics Data System (ADS)

    D'Hulst, R.; Rodgers, G. J.

    2001-10-01

    In a recent work, we introduced two models for the dynamics of customers trying to find the business that best corresponds to their expectation for the price of a commodity. In agreement with the empirical data, a power-law distribution for the business sizes was obtained, taking the number of customers of a business as a proxy for its size. Here, we extend one of our previous models in two different ways. First, we introduce a business aggregation rate that is fitness dependent, which allows us to reproduce a spread in empirical data from one country to another. Second, we allow the bankruptcy rate to take a different functional form, to be able to obtain a log-normal distribution with power-law tails for the size of the businesses.

  15. Distribution over pore radii in random and isotropic systems of polydisperse rods with finite aspect ratios

    NASA Astrophysics Data System (ADS)

    Chatterjee, Avik P.

    2016-06-01

    Excluded-volume arguments are applied toward modeling the pore-size distribution in systems of randomly arranged cylindrical rods with finite and nonuniform aspect ratios. An explicit expression for the pore-size distribution is obtained by way of an analogy to a hypothetical system of fully penetrable objects, through a mapping that is designed to preserve the volume fraction occupied by the particle cores and the specific surface area. Results are presented for the mean value and standard deviation of the pore radius as functions of the rod aspect ratio, volume fraction, and polydispersity (degree of nonuniformity in the aspect ratios of the particles).

  16. Effects of pore size in 3-D fibrous matrix on human trophoblast tissue development.

    PubMed

    Ma, T; Li, Y; Yang, S T; Kniss, D A

    2000-12-20

    The effects of pore size in a 3-D polyethylene terephthalate (PET) nonwoven fibrous matrix on long-term tissue development of human trophoblast ED27 cells were studied. Thermal compression was used to modify the porosity and pore size of the PET matrix. The pore size distributions in PET matrices were quantified using a liquid extrusion method. Cell metabolic activities, estradiol production, and cell proliferation and differentiation were studied for ED27 cells cultured in the thermally compressed PET matrices with known pore structure characteristics. In general, metabolic activities and proliferation rate were higher initially for cultures grown in the low-porosity (LP) PET matrix (porosity of 0.849, average pore size of 30 microm in diameter) than those in the high-porosity (HP) matrix (porosity of 0.896, average pore size of 39 microm in diameter). However, 17beta-estradiol production and cell differentiation activity in the HP matrix surpassed those in the LP matrix after 12 days. The expression levels of cyclin B1 and p27kip1 in cells revealed progressively decreasing proliferation and increasing differentiation activities for cells grown in PET matrices. Also, difference in pore size controlled the cell spatial organization in the PET matrices and contributed to the tissue development in varying degrees of proliferation and differentiation. It was also found that cells grown on the 2-D surface behaved differently in cell cycle progression and did not show increased differentiation activities after growth had stopped and proliferation activities had lowered to a minimal level. The results from this study suggest that the 3-D cell organization guided by the tissue scaffold is important to tissue formation in vitro. PMID:11064329

  17. Effects of Pore Distributions on Ductility of Thin-Walled High Pressure Die-Cast Magnesium

    SciTech Connect

    Choi, Kyoo Sil; Li, Dongsheng; Sun, Xin; Li, Mei; Allison, John

    2013-06-01

    In this paper, a microstructure-based three-dimensional (3D) finite element modeling method is adopted to investigate the effects of porosity in thin-walled high pressure die-cast (HPDC) Magnesium alloys on their ductility. For this purpose, the cross-sections of AM60 casting samples are first examined using optical microscope and X-ray tomography to obtain the general information on the pore distribution features. The experimentally observed pore distribution features are then used to generate a series of synthetic microstructure-based 3D finite element models with different pore volume fractions and pore distribution features. Shear and ductile damage models are adopted in the finite element analyses to induce the fracture by element removal, leading to the prediction of ductility. The results in this study show that the ductility monotonically decreases as the pore volume fraction increases and that the effect of ‘skin region’ on the ductility is noticeable under the condition of same local pore volume fraction in the center region of the sample and its existence can be beneficial for the improvement of ductility. The further synthetic microstructure-based 3D finite element analyses are planned to investigate the effects of pore size and pore size distribution.

  18. Scaffold pore size modulates in vitro osteogenesis of human adipose-derived stem/stromal cells.

    PubMed

    Huri, Pinar Yilgor; Ozilgen, B Arda; Hutton, Daphne L; Grayson, Warren L

    2014-08-01

    Trabecular bone has an interconnected porous structure, which influences cellular responses, biochemical transport and mechanical strength. Appropriately mimicking this structural organization in biomaterial scaffolds can facilitate more robust bone tissue regeneration and integration by providing a native microenvironment to the cells. This study examined the effect of pore size on human adipose-derived stem/stromal cell (ASC) osteogenesis within poly(ε-caprolactone) (PCL) scaffolds. Scaffold pore size was controlled by porogen leaching of custom-made paraffin particles with three different size ranges: P200 (< 500 µm), P500 (500-1000 µm), and P1000 (1000-1500 µm). Scaffolds produced by leaching these particles exhibited highly interconnected pores and rough surface structures that were favorable for cell attachment and ingrowth. The osteogenic response of ASCs was evaluated following 3 weeks of in vitro culture using biochemical (ALP, Ca(2+)/DNA content), mechanical (compression test) and histological (H&E and von Kossa staining) analyses. It was observed that while the total number of cells was similar for all scaffolds, the cell distributions and osteogenic properties were affected by the scaffold pore size. ASCs were able to bridge smaller pores and grow uniformly within these scaffolds (P200) while they grew as a layer along the periphery of the largest pores (P1000). The cell-biomaterial interactions specific to the latter case led to enhanced osteogenic responses. The ALP activity and Ca(2+) deposition were doubled in P1000 scaffolds as compared to P200 scaffolds. A significant difference was observed between the compressive strength of unseeded and seeded P1000 scaffolds. Therefore, we demonstrated that the use of scaffolds with pores that are in the range of 1 mm enhances in vitro ASC osteogenesis, which may improve their performance in engineered bone substitutes. PMID:24945873

  19. Facile fabrication of BiVO4 nanofilms with controlled pore size and their photoelectrochemical performances

    NASA Astrophysics Data System (ADS)

    Feng, Chenchen; Jiao, Zhengbo; Li, Shaopeng; Zhang, Yan; Bi, Yingpu

    2015-12-01

    We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures.We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06584d

  20. Experimental study on pore distribution characters and convert rate of CaO

    NASA Astrophysics Data System (ADS)

    Jia, Li; Zeng, Yanyan; Zhang, Tao

    2005-03-01

    During the reaction between calcium sorbents and SO2, calcium sorbents are first calcined and converted into CaO. CaO can be obtained by calcining Ca(OH)2 or CaCO3. The porosity of the sorbent is increased because of calcination and is decreased because of sulfurization. In the calcination process H2O or CO2 is escaped from the particles and pores are formed in particles. The reaction or convert rate of CaO is influenced strongly by the pore structure characters. From Ca(OH)2 to CaO the escape velocity of H2O or its mass transfer is one of the key factors influencing the pore forming. During calcination process different heating velocity, different heating time and temperature were suggested. The temperature rising rate and calcining temperature play important role to the pore structure. The convert rates of CaO obtained through different calcining conditions were investigated experimentally. Some interesting results were showed that the calcium utilization of CaO particles is determined not only by the special surface area and total pore volume, but also by pore-size distribution. The main factor influencing the sulfation is the pore diameter distribution at lower sulfation temperature. For higher reaction temperature specific volume is the important reason. But pore-size distribution is strongly influenced by heat flux and temperature in the calcining process.

  1. Hail Size Distribution Mapping

    NASA Technical Reports Server (NTRS)

    2008-01-01

    A 3-D weather radar visualization software program was developed and implemented as part of an experimental Launch Pad 39 Hail Monitor System. 3DRadPlot, a radar plotting program, is one of several software modules that form building blocks of the hail data processing and analysis system (the complete software processing system under development). The spatial and temporal mapping algorithms were originally developed through research at the University of Central Florida, funded by NASA s Tropical Rainfall Measurement Mission (TRMM), where the goal was to merge National Weather Service (NWS) Next-Generation Weather Radar (NEXRAD) volume reflectivity data with drop size distribution data acquired from a cluster of raindrop disdrometers. In this current work, we adapted these algorithms to process data from a cluster of hail disdrometers positioned around Launch Pads 39A or 39B, along with the corresponding NWS radar data. Radar data from all NWS NEXRAD sites is archived at the National Climatic Data Center (NCDC). That data can be readily accessed at . 3DRadPlot plots Level III reflectivity data at four scan elevations (this software is available at Open Channel Software, ). By using spatial and temporal interpolation/extrapolation based on hydrometeor fall dynamics, we can merge the hail disdrometer array data coupled with local Weather Surveillance Radar-1988, Doppler (WSR-88D) radial velocity and reflectivity data into a 4-D (3-D space and time) picture of hail size distributions. Hail flux maps can then be generated and used for damage prediction and assessment over specific surfaces corresponding to structures within the disdrometer array volume. Immediately following a hail storm, specific damage areas and degree of damage can be identified for inspection crews.

  2. Pore size engineering applied to the design of separators for nickel-hydrogen cells and batteries

    NASA Technical Reports Server (NTRS)

    Abbey, K. M.; Britton, D. L.

    1983-01-01

    Pore size engineering in starved alkaline multiplate cells involves adopting techniques to widen the volume tolerance of individual cells. Separators with appropriate pore size distributions and wettability characteristics (capillary pressure considerations) to have wider volume tolerances and an ability to resist dimensional changes in the electrodes were designed. The separators studied for potential use in nickel-hydrogen cells consist of polymeric membranes as well as inorganic microporous mats. In addition to standard measurements, the resistance and distribution of electrolyte as a function of total cell electrolyte content were determined. New composite separators consisting of fibers, particles and/or binders deposited on Zircar cloth were developed in order to engineer the proper capillary pressure characteristics in the separator. These asymmetric separators were prepared from a variety of fibers, particles and binders. Previously announced in STAR as N83-24571

  3. Pore size engineering applied to the design of separators for nickel-hydrogen cells and batteries

    NASA Technical Reports Server (NTRS)

    Abbey, K. M.; Britton, D. L.

    1983-01-01

    Pore size engineering in starved alkaline multiplate cells involves adopting techniques to widen the volume tolerance of individual cells. Separators with appropriate pore size distributions and wettability characteristics (capillary pressure considerations) to have wider volume tolerances and an ability to resist dimensional changes in the electrodes were designed. The separators studied for potential use in nickel-hydrogen cells consist of polymeric membranes as well as inorganic microporous mats. In addition to standard measurements, the resistance and distribution of electrolyte as a function of total cell electrolyte content were determined. New composite separators consisting of fibers, particles and/or binders deposited on Zircar cloth were developed in order to engineer the proper capillary pressure characteristics in the separator. These asymmetric separators were prepared from a variety of fibers, particles and binders.

  4. Experimental evidence of the role of pores on movement and distribution of bacteria in soil

    NASA Astrophysics Data System (ADS)

    Kravchenko, Alexandra N.; Rose, Joan B.; Marsh, Terence L.; Guber, Andrey K.

    2014-05-01

    It has been generally recognized that micro-scale heterogeneity in soil environments can have a substantial effect on movement, fate, and survival of soil microorganisms. However, only recently the development of tools for micro-scale soil analyses, including X-ray computed micro-tomography (μ-CT), enabled quantitative analyses of these effects. The long-term goal of our work is to explore how differences in micro-scale characteristics of pore structures influence movement, spatial distribution patterns, and activities of soil microorganisms. Using X-ray μ-CT we found that differences in land use and management practices lead to development of contrasting patterns in pore size-distributions within intact soil aggregates. Then our experiments with Escherichia coli added to intact soil aggregates demonstrated that the differences in pore structures can lead to substantial differences in bacteria redistribution and movement within the aggregates. Specifically, we observed more uniform E.coli redistribution in aggregates with homogeneously spread pores, while heterogeneous pore structures resulted in heterogeneous E.coli patterns. Water flow driven by capillary forces through intact aggregate pores appeared to be the main contributor to the movement patterns of the introduced bacteria. Influence of pore structure on E.coli distribution within the aggregates further continued after the aggregates were subjected to saturated water flow. E. coli's resumed movement with saturated water flow and subsequent redistribution within the soil matrix was influenced by porosity, abundance of medium and large pores, pore tortuosity, and flow rates, indicating that greater flow accompanied by less convoluted pores facilitated E. coli transport within the intra-aggregate space. We also found that intra-aggregate heterogeneity of pore structures can have an effect on spatial distribution patterns of indigenous microbial populations. Preliminary analysis showed that in aggregates from

  5. Improving prediction of hydraulic conductivity by constraining capillary bundle models to a maximum pore size

    NASA Astrophysics Data System (ADS)

    Iden, Sascha C.; Peters, Andre; Durner, Wolfgang

    2015-11-01

    The prediction of unsaturated hydraulic conductivity from the soil water retention curve by pore-bundle models is a cost-effective and widely applied technique. One problem for conductivity predictions from retention functions with continuous derivatives, i.e. continuous water capacity functions, is that the hydraulic conductivity curve exhibits a sharp drop close to water saturation if the pore-size distribution is wide. So far this artifact has been ignored or removed by introducing an explicit air-entry value into the capillary saturation function. However, this correction leads to a retention function which is not continuously differentiable. We present a new parameterization of the hydraulic properties which uses the original saturation function (e.g. of van Genuchten) and introduces a maximum pore radius only in the pore-bundle model. In contrast to models using an explicit air entry, the resulting conductivity function is smooth and increases monotonically close to saturation. The model concept can easily be applied to any combination of retention curve and pore-bundle model. We derive closed-form expressions for the unimodal and multimodal van Genuchten-Mualem models and apply the model concept to curve fitting and inverse modeling of a transient outflow experiment. Since the new model retains the smoothness and continuous differentiability of the retention model and eliminates the sharp drop in conductivity close to saturation, the resulting hydraulic functions are physically more reasonable and ideal for numerical simulations with the Richards equation or multiphase flow models.

  6. Potts model simulation of grain size distributions during final stage sintering

    SciTech Connect

    Zeng, P.; Tikare, V.

    1998-09-01

    The Potts Monte Carlo model was used to simulate microstructural evolution and characterize grain size distribution during the final stages of sintering. Simultaneous grain growth, pore migration and pore shrinkage were simulated in a system with an initial porosity of 10% with varying ratios of grain boundary mobility to pore shrinkage rates. This investigation shows that the presence of pores changes the grain size distribution and the topological characteristics due to pinning of grains by pores. As pores shrink away, their pinning effect decreases. Once pore shrinkage is complete, normal grain growth is achieved.

  7. Determining the dynamic range of MCPs based on pore size and strip current

    NASA Astrophysics Data System (ADS)

    Hunt, C.; Adrian, M. L.; Herrero, F.; James, P.; Jones, H. H.; Rodriguez, M.; Roman, P.; Shappirio, M.

    2010-12-01

    Micro-Channel Plates (MCPs) are used as detectors for almost all detectors measuring particles (both ions, electrons and neutrals) below 30 keV. Recent advances in the manufacturing technology of the MCPs have increased the number of options one has when selecting plates for an instrument. But it is not clear how many of these options affect the performance of the MCPs. In particular the dynamic range is not a clear cut calculation to make from the strip current. There is also some evidence that pore size and coating play a role. We measured the dynamic range and pulse height distribution of MCPs detector chevron stacks with a wide variety of strip currents from the low “normal” range in the EDR range. We also looked at the effects of varying the pore size from 25 microns to 10 microns, partial plating of the MCP surface and coating one surface on each MCP with gold rather than the standard zinc chromium. We will show how the dynamic range and pulse height distributions vary vs. strip current, pore size, and surface plating configurations.

  8. Pore size and pore throat types in a heterogeneous dolostone reservoir, Devonian Grosmont formation, western Canada sedimentary basin

    SciTech Connect

    Luo, P.; Machel, H. G.

    1995-11-01

    The Devonian Grosmont Formation in northeastern Alberta, Canada, is a giant heavy-oil reservoir. The main reservoir rocks are dolomitized and karstified platform and ramp carbonates, and the best reservoir facies occur in the upper Grosmont (UGM) units 3 and 2. In these units, reservoir properties are highly heterogeneous. Hand specimen, thin section, UV, and SEM petrography, as well as grading scales, mercury capillary pressure curve analysis, and statistics, have been used to characterize reservoir heterogeneity. Our investigation led to a new pore size classification for carbonate reservoirs; this new classification has four pore sizes: microporosity (pore diameters <1 {mu}m), mesoporosity (pore diameters 1-1000 {mu}m), macroporosity (pore diameters 1-256 mm), and megaporosity (pore diameters >256 mm). A combination of microscopic observations and capillary pressure curve characteristics led to the recognition of four pore throat texture types on the microporosity scale, and to five types on the mesoporosity scale. Microporosity pore types include (1) intracrystal dissolution porosity, (2) pervasive intercrystal and intracrystal dissolution porosity, (3) intergranular and/or intercrystal porosity in grainstones, and (4) primary or solution microporosity in mud matrix (only in limestones). Mesoporosity pore types include (1) intercrystal porosity, (2) solution-enhanced intercrystal porosity, (3) oversized porosity, (4) intragranular solution porosity, and (5) intergranular solution porosity. Some of these types are homogeneous (e.g., non-fabric selective dissolution porosity and intercrystal primary porosity), whereas others are heterogeneous. Generally, hydrocarbon recovery efficiency is good in the homogeneous pore throat types, but poor in the heterogeneous types.

  9. Nuclear magnetic resonance pore size determination for unconsolidated sediments with strong internal gradients

    NASA Astrophysics Data System (ADS)

    Duschl, M.; Pohlmeier, A. J.; Galvosas, P.; Vereecken, H.

    2014-12-01

    Water distribution and flow within porous media are mainly controlled by the pore space structure. Well established methods for the determination of pore sizes like multistep outflow and gas adsorption isotherms (BET) are often time consuming, expensive, or produce toxic waste. As an alternative fast and non-destructive technique, nuclear magnetic resonance (NMR) is used because it probes hydrogen and therefore the dynamics and interactions of water. Pore space is most easily characterized by NMR relaxometry where the total relaxation rate is controlled by the surface relaxivity ρ of the porous medium in combination with the surface-to-volume ratio (S/V) [1]. Furthermore, there are contributions of molecular diffusion through local magnetic field gradients which are created by susceptibility differences between solid and liquid phases [2] as well as by paramagnetic impurities [3]. Hence, surface to volume ratios and surface relaxivities of porous media cannot be measured individually with NMR relaxometry. Therefore, NMR diffusion measurements are applied to probe the S/V of pores without other contributions. In this study, we demonstrate that NMR diffusion measurements are feasible to determine the S/V ratio of the pore space of quartz sand coated with goethite (α-FeOOH) as paramagnetic impurity. Our findings were compared to BET measurements and we found no dependence of the S/V on the coating density with NMR diffusion and a clear dependence between coating density and S/V with krypton BET measurements. Possible explanations are the different characteristic length scales on which the pore space is probed, and the intrinsic fractal nature of porous media [4] together with the roughness of the pore surface on a nm-scale due to the coating process. After isolating the additional contribution of the paramagnetic impurities to the NMR relaxation and the calibration of the NMR relaxation signal for each coating density it was possible to use fast relaxometry

  10. Pore space analysis of NAPL distribution in sand-clay media

    USGS Publications Warehouse

    Matmon, D.; Hayden, N.J.

    2003-01-01

    This paper introduces a conceptual model of clays and non-aqueous phase liquids (NAPLs) at the pore scale that has been developed from a mathematical unit cell model, and direct micromodel observation and measurement of clay-containing porous media. The mathematical model uses a unit cell concept with uniform spherical grains for simulating the sand in the sand-clay matrix (???10% clay). Micromodels made with glass slides and including different clay-containing porous media were used to investigate the two clays (kaolinite and montmorillonite) and NAPL distribution within the pore space. The results were used to understand the distribution of NAPL advancing into initially saturated sand and sand-clay media, and provided a detailed analysis of the pore-scale geometry, pore size distribution, NAPL entry pressures, and the effect of clay on this geometry. Interesting NAPL saturation profiles were observed as a result of the complexity of the pore space geometry with the different packing angles and the presence of clays. The unit cell approach has applications for enhancing the mechanistic understanding and conceptualization, both visually and mathematically, of pore-scale processes such as NAPL and clay distribution. ?? 2003 Elsevier Science Ltd. All rights reserved.

  11. Two micron pore size MCP-based image intensifiers

    NASA Astrophysics Data System (ADS)

    Glesener, John; Estrera, Joseph

    2010-02-01

    Image intensifiers (I2) have many advantages as detectors. They offer single photon sensitivity in an imaging format, they're light in weight and analog I2 systems can operate for hours on a single AA battery. Their light output is such as to exploit the peak in color sensitivity of the human eye. Until recent developments in CMOS sensors, they also were one of the highest resolution sensors available. The closest all solid state solution, the Texas Instruments Impactron chip, comes in a 1 megapixel format. Depending on the level of integration, an Impactron based system can consume 20 to 40 watts in a system configuration. In further investing in I2 technology, L-3 EOS determined that increasing I2 resolution merited a high priority. Increased I2 resolution offers the system user two desirable options: 1) increased detection and identification ranges while maintaining field-of-view (FOV) or 2) increasing FOV while maintaining the original system resolution. One of the areas where an investment in resolution is being made is in the microchannel plate (MCP). Incorporation of a 2 micron MCP into an image tube has the potential of increasing the system resolution of currently fielded systems. Both inverting and non-inverting configurations are being evaluated. Inverting tubes are being characterized in night vision goggle (NVG) and sights. The non-inverting 2 micron tube is being characterized for high resolution I2CMOS camera applications. Preliminary measurements show an increase in the MTF over a standard 5 micron pore size, 6 micron pitch plate. Current results will be presented.

  12. Lunar soil grain size distribution

    NASA Technical Reports Server (NTRS)

    Carrier, W. D., III

    1973-01-01

    A comprehensive review has been made of the currently available data for lunar grain size distributions. It has been concluded that there is little or no statistical difference among the large majority of the soil samples from the Apollo 11, 12, 14, and 15 missions. The grain size distribution for these soils has reached a steady state in which the comminution processes are balanced by the aggregation processes. The median particle size for the steady-state soil is 40 to 130 microns. The predictions of lunar grain size distributions based on the Surveyor television photographs have been found to be quantitatively in error and qualitatively misleading.

  13. A general diagram for estimating pore size of ultrafiltration and reverse osmosis membranes

    NASA Technical Reports Server (NTRS)

    Sarbolouki, M. N.

    1982-01-01

    A slit sieve model has been used to develop a general correlation between the average pore size of the upstream surface of a membrane and the molecular weight of the solute which it retains by better than 80%. The pore size is determined by means of the correlation using the high retention data from an ultrafiltration (UF) or a reverse osmosis (RO) experiment. The pore population density can also be calculated from the flux data via appropriate equations.

  14. Discontinuous pore fluid distribution under microgravity--KC-135 flight investigations.

    PubMed

    Reddi, Lakshmi N; Xiao, Ming; Steinberg, Susan L

    2005-01-01

    Designing a reliable plant growth system for crop production in space requires the understanding of pore fluid distribution in porous media under microgravity. The objective of this experimental investigation, which was conducted aboard NASA KC-135 reduced gravity flight, is to study possible particle separation and the distribution of discontinuous wetting fluid in porous media under microgravity. KC-135 aircraft provided gravity conditions of 1, 1.8, and 10(-2) g. Glass beads of a known size distribution were used as porous media; and Hexadecane, a petroleum compound immiscible with and lighter than water, was used as wetting fluid at residual saturation. Nitrogen freezer was used to solidify the discontinuous Hexadecane ganglia in glass beads to preserve the ganglia size changes during different gravity conditions, so that the blob-size distributions (BSDs) could be measured after flight. It was concluded from this study that microgravity has little effect on the size distribution of pore fluid blobs corresponding to residual saturation of wetting fluids in porous media. The blobs showed no noticeable breakup or coalescence during microgravity. However, based on the increase in bulk volume of samples due to particle separation under microgravity, groups of particles, within which pore fluid blobs were encapsulated, appeared to have rearranged themselves under microgravity. PMID:16052743

  15. Discontinuous pore fluid distribution under microgravity--KC-135 flight investigations

    NASA Technical Reports Server (NTRS)

    Reddi, Lakshmi N.; Xiao, Ming; Steinberg, Susan L.

    2005-01-01

    Designing a reliable plant growth system for crop production in space requires the understanding of pore fluid distribution in porous media under microgravity. The objective of this experimental investigation, which was conducted aboard NASA KC-135 reduced gravity flight, is to study possible particle separation and the distribution of discontinuous wetting fluid in porous media under microgravity. KC-135 aircraft provided gravity conditions of 1, 1.8, and 10(-2) g. Glass beads of a known size distribution were used as porous media; and Hexadecane, a petroleum compound immiscible with and lighter than water, was used as wetting fluid at residual saturation. Nitrogen freezer was used to solidify the discontinuous Hexadecane ganglia in glass beads to preserve the ganglia size changes during different gravity conditions, so that the blob-size distributions (BSDs) could be measured after flight. It was concluded from this study that microgravity has little effect on the size distribution of pore fluid blobs corresponding to residual saturation of wetting fluids in porous media. The blobs showed no noticeable breakup or coalescence during microgravity. However, based on the increase in bulk volume of samples due to particle separation under microgravity, groups of particles, within which pore fluid blobs were encapsulated, appeared to have rearranged themselves under microgravity.

  16. Microporous polyphenylenes with tunable pore size for hydrogen storage.

    SciTech Connect

    Yuan, S.; Dorney, B.; White, D.; Kirklin, S.; Zapol, P.; Yu, L.; Liu, D. J.; Univ. of Chicago

    2010-01-01

    A series of highly porous polymers with similar BET surface areas of higher than 1000 m2 g-1 but tunable pore ranging from 0.7 nm to 0.9 nm were synthesized through facile ethynyl trimerization reaction to demonstrate the surface property-hydrogen adsorption relationship.

  17. Effect on the Pore-Size Dependence of an Organic Electrolyte Supercapacitor

    SciTech Connect

    Jiang, Deen; Jin, Zhehui; Henderson, Douglous; Wu, Jianzhong

    2012-01-01

    Organic electrolytes such as tetraethylammonium tetrafluoroborate dissolved in acetonitrile (TEA-BF{sub 4}/ACN) are widely used in commercial supercapacitors and academic research, but conflicting experimental results have been reported regarding the dependence of surface-area-normalized capacitance on the pore size. Here we show from a classical density functional theory the dependence of capacitance on the pore size from 0.5 to 3.0 nm for a model TEA-BF{sub 4}/ACN electrolyte. We find that the capacitance-pore size curve becomes roughly flat after the first peak around the ion diameter, and the peak capacitance is not significantly higher than the large-pore average. We attribute the invariance of capacitance with the pore size to the formation of an electric double-layer structure that consists of counterions and highly organized solvent molecules. This work highlights the role of the solvent molecules in modulating the capacitance and reconciles apparently conflicting experimental reports.

  18. Hydrogen Storage Properties of Rigid Three-Dimensional Hofmann Clathrate Derivatives: The Effects of Pore Size

    SciTech Connect

    Culp, J.T.; Natesakhawat, Sittichai; Smith, M.R.; Bittner, E.; Matranga, C.S.; Bockrath, B.

    2008-05-01

    The effects of pore size on the hydrogen storage properties of a series of pillared layered solids based on the M(L)[M'(CN)4] structural motif, where M ) Co or Ni, L ) pyrazine (pyz), 4,4'-bipyridine (bpy), or 4,4'-dipyridylacetylene (dpac), and M' ) Ni, Pd, or Pt, has been investigated. The compounds all possess slitlike pores with constant in-plane dimensions and similar organic functionality. The pore heights vary as a function of L and provide a means for a systematic investigation of the effects of pore dimension on hydrogen storage properties in porous materials. Hydrogen isotherms were measured at 77 and 87 K up to a pressure of 1 atm. The pyz pillared materials with the smallest pore dimensions store hydrogen at a pore density similar to that of liquid hydrogen. The adsorbed hydrogen density drops by a factor of 2 as the relative pore size is tripled in the dpac material. The decreased storage efficiency diminishes the expected gravimetric gain in capacity for the larger pore materials. The heats of adsorption were found to range from 6 to 8 kJ/mol in the series and weakly correlate with pore size.

  19. IMPACT OF COMPOSITION AND HEAT TREATMENT ON PORE SIZE IN POROUS WALLED HOLLOW GLASS MICROSPHERES

    SciTech Connect

    Raszewski, F; Erich Hansen, E; Ray Schumacher, R; David Peeler, D

    2007-12-04

    The Savannah River National Laboratory (SRNL) developed a new geometric form: hollow glass microspheres (HGMs), with unique porous walls. The new geometric form combines the existing technology of HGMs with basic glass science knowledge in the realm of glass-in-glass phase separation. Conceptually, the development of a HGM with porous walls (referred to as a PWHGM) provides a unique system in which various media or filling agents can be incorporated into the PWHGM (via transport through the porous walls) and ultimately has the capacity to serve as a functional delivery system in various industrial applications. Applications of these types of systems could range from hydrogen storage, molecular sieves, drug and bioactive delivery systems, to environmental, chemical and biological indicators, relevant to Energy, Environmental Processing and Homeland Security fields. As a specific example, previous studies at SRNL have introduced materials capable of hydrogen storage (as well as other materials) into the interior of the PWHGMs. The goal of this project was to determine if the microstructure (i.e., pore size and pore size distribution) of a PWHGM could be altered or tailored by varying composition and/or heat treatment (time and/or temperature) conditions. The ability to tailor the microstructure through composition or heat treatments could provide the opportunity to design the PWHGM system to accommodate different additives or fill agents. To meet this objective, HGMs of various alkali borosilicate compositions were fabricated using a flame forming apparatus installed at the Aiken County Technical Laboratory (ACTL). HGMs were treated under various heat treatment conditions to induce and/or enhance glass in glass phase separation. Heat treatment temperatures ranged from 580 C to 620 C, while heat treatment times were either 8 or 24 hours. Of the two primary variables assessed in this study, heat treatment temperature was determined to be most effective in changing the

  20. Centaur size distribution with DECam

    NASA Astrophysics Data System (ADS)

    Fuentes, Cesar; Trilling, David E.; Schlichting, Hilke

    2014-11-01

    We present the results of the 2014 centaur search campaign on the Dark Energy Camera (DECam) in Tololo, Chile. This is the largest debiased Centaur survey to date, measuring for the first time the size distribution of small Centaurs (1-10km) and the first time the sizes of planetesimals from which the entire Solar System formed are directly detected.The theoretical model for the coagulation and collisional evolution of the outer solar system proposed in Schlichting et al. 2013 predicts a steep rise in the size distribution of TNOs smaller than 10km. These objects are below the detection limit of current TNO surveys but feasible for the Centaur population. By constraining the number of Centaurs and this feature in their size distribution we can confirm the collisional evolution of the Solar System and estimate the rate at which material is being transferred from the outer to the inner Solar System. If the shallow power law behavior from the TNO size distribution at ~40km can be extrapolated to 1km, the size of the Jupiter Family of Comets (JFC), there would not be enough small TNOs to supply the JFC population (Volk & Malhotra, 2008), debunking the link between TNOs and JFCs.We also obtain the colors of small Centaurs and TNOs, providing a signature of collisional evolution by measuring if there is in fact a relationship between color and size. If objects smaller than the break in the TNO size distribution are being ground down by collisions then their surfaces should be fresh, and then appear bluer in the optical than larger TNOs that are not experiencing collisions.

  1. Pore Scale Heterogeneity in the Mineral Distribution and Surface Area of Porous Rocks

    NASA Astrophysics Data System (ADS)

    Lai, Peter; Krevor, Sam

    2015-04-01

    An important control on rate of interfacial processes between minerals and aqueous solutions such as nucleation of solids, and mineral dissolution and growth is reactive surface area. In geochemical modelling, the continuum hypothesis is based on the assumption that the system can be represented by a sufficiently large number of representative elemental volumes. There has been recent interest in studying the impact of this assumption on reaction-transport coupled systems. In this study, the impact of pore-scale heterogeneity on the distribution of reactive surface area is discussed. 3D images obtained using x-ray micro-tomography were used to characterise the distribution of reactive surface area. The results were compared to independent observations. Mineral identification using x- ray diffraction and fluorescence suggested general agreement with CT analysis. Nitrogen BET surface areas were one to two orders of magnitude higher than measurements from x-ray imagery. Co- registered images of Berea sandstone from x-ray and energy dispersive spectroscopy imagery suggested that quartz, K-feldspar and most clays could be identified. However, minor minerals such as albite and illite did not exhibit enough contrast. In Berea sandstone, mineral surface area fraction was poorly correlated to the mineral volumetric fraction. Clay and feldspar minerals exhibited higher surface area fractions than bulk mineralogy suggested. In contrast, in the Edwards carbonate samples, modal mineral composition correlated with mineral-specific surface area. Berea sandstone revealed a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. Conversely, the carbonate samples suggested a continuous range of pore sizes across length scales. A comparison with pore network model simulations from the literature was made. First order estimates of mineral specific correlations between geometric area measured in the x-ray images were used to convert the CT

  2. Pore-size dependent effects on structure and vibrations of 1-ethyl-3-methylimidazolium tetrafluoroborate in nanoporous carbon

    NASA Astrophysics Data System (ADS)

    Thürmer, Stephan; Kobayashi, Yoshikazu; Ohba, Tomonori; Kanoh, Hirofumi

    2015-09-01

    We report XRD and IR measurements of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4) adsorbed in activated carbons, molecular sieving carbon, and single wall carbon nanohorn, where we specifically chose a wide range of pore sizes from 0.5 nm to 2.5 nm. Electron radial distribution function analysis reveals denser packing upon adsorption in two steps, for pore widths larger and comparable to the ion size. Average ion-distance was decreased by 0.05 nm in the latter case. With support of DFT calculations we identify a suppression of specific vibrational modes, which are interpreted as constrainment by the pore walls. Possible consequences for supercapacitor application are discussed.

  3. Pore Distribution and Water Uptake in a Cenosphere-Cement Paste Composite Material

    NASA Astrophysics Data System (ADS)

    Baronins, J.; Setina, J.; Sahmenko, G.; Lagzdina, S.; Shishkin, A.

    2015-11-01

    Alumina silicate cenospheres (CS) is a significant waste material from power plants that use a coal. Use CS as Portland cement replacement material gives opportunity to control physical and mechanical properties and makes a product lighter and more cost-effective. In the frame of this study, Portland cement paste samples were produced by adding CS in the concentration range from 0 to 40 volume %. Water uptake of hardened samples was checked and pore size distribution by using the mercury porosimetry was determined. In a cold climate where the temperature often falls below 0 °C, it is important to avoid the amount of micrometer sized pores in the final structure and to decrease water absorption capacity of material. In winter conditions, water fills such pores and causes additional stresses to their walls by expansion while freezing. It was found that generally water uptake capacity for cement paste samples decreased up to 20% by increasing the concentration of CS up to 40 volume %, at the same time, the volume of micrometer sized opened pores increases.

  4. Controlling internal pore sizes in bicontinuous polymeric nanospheres.

    PubMed

    McKenzie, Beulah E; Friedrich, Heiner; Wirix, Maarten J M; de Visser, Joël F; Monaghan, Olivia R; Bomans, Paul H H; Nudelman, Fabio; Holder, Simon J; Sommerdijk, Nico A J M

    2015-02-16

    Complex polymeric nanospheres were formed in water from comb-like amphiphilic block copolymers. Their internal morphology was determined by three-dimensional cryo-electron tomographic analysis. Varying the polymer molecular weight (MW) and the hydrophilic block weight content allowed for fine control over the internal structure. Construction of a partial phase diagram allowed us to determine the criteria for the formation of bicontinuous polymer nanosphere (BPN), namely for copolymers with MW of up to 17 kDa and hydrophilic weight fractions of ≤0.25; and varying the organic solvent to water ratio used in their preparation allowed for control over nanosphere diameters from 70 to 460 nm. Significantly, altering the block copolymer hydrophilic-hydrophobic balance enabled control of the internal pore diameter of the BPNs from 10 to 19 nm. PMID:25640026

  5. Controlling Internal Pore Sizes in Bicontinuous Polymeric Nanospheres**

    PubMed Central

    McKenzie, Beulah E; Friedrich, Heiner; Wirix, Maarten J M; de Visser, Joël F; Monaghan, Olivia R; Bomans, Paul H H; Nudelman, Fabio; Holder, Simon J; Sommerdijk, Nico A J M

    2015-01-01

    Complex polymeric nanospheres were formed in water from comb-like amphiphilic block copolymers. Their internal morphology was determined by three-dimensional cryo-electron tomographic analysis. Varying the polymer molecular weight (MW) and the hydrophilic block weight content allowed for fine control over the internal structure. Construction of a partial phase diagram allowed us to determine the criteria for the formation of bicontinuous polymer nanosphere (BPN), namely for copolymers with MW of up to 17 kDa and hydrophilic weight fractions of ≤0.25; and varying the organic solvent to water ratio used in their preparation allowed for control over nanosphere diameters from 70 to 460 nm. Significantly, altering the block copolymer hydrophilic–hydrophobic balance enabled control of the internal pore diameter of the BPNs from 10 to 19 nm. PMID:25640026

  6. Detection, 3-D positioning, and sizing of small pore defects using digital radiography and tracking

    NASA Astrophysics Data System (ADS)

    Lindgren, Erik

    2014-12-01

    This article presents an algorithm that handles the detection, positioning, and sizing of submillimeter-sized pores in welds using radiographic inspection and tracking. The possibility to detect, position, and size pores which have a low contrast-to-noise ratio increases the value of the nondestructive evaluation of welds by facilitating fatigue life predictions with lower uncertainty. In this article, a multiple hypothesis tracker with an extended Kalman filter is used to track an unknown number of pore indications in a sequence of radiographs as an object is rotated. Each pore is not required to be detected in all radiographs. In addition, in the tracking step, three-dimensional (3-D) positions of pore defects are calculated. To optimize, set up, and pre-evaluate the algorithm, the article explores a design of experimental approach in combination with synthetic radiographs of titanium laser welds containing pore defects. The pre-evaluation on synthetic radiographs at industrially reasonable contrast-to-noise ratios indicate less than 1% false detection rates at high detection rates and less than 0.1 mm of positioning errors for more than 90% of the pores. A comparison between experimental results of the presented algorithm and a computerized tomography reference measurement shows qualitatively good agreement in the 3-D positions of approximately 0.1-mm diameter pores in 5-mm-thick Ti-6242.

  7. Pore scale heterogeneity in the mineral distribution and reactive surface area of rocks

    NASA Astrophysics Data System (ADS)

    Lai, P. E.; Krevor, S. C.

    2013-12-01

    There are long-standing challenges in characterizing reactive transport in porous media at scales larger than individual pores. This hampers the prediction of the field-scale impact of geochemical processes on fluid flow [1]. This is a source of uncertainty for CO2 injection, which results in a reactive fluid-rock system, particularly in carbonate rock reservoirs. A potential cause is the inability of the continuum approach to incorporate the impact of heterogeneity in pore-scale reaction rates. This results in part from pore-scale heterogeneities in surface area of reactive minerals [2,3]. In this study we have created μm resolution 3D images of 3 sandstone and 4 carbonate rocks using x-ray microtomography. Using in-house image processing techniques and auxiliary characterisation with thin section, electron microscope and spectroscopic techniques we quantified the surface area of each mineral phase in the x-ray CT images. This quantification was validated against N2 BET surface area and He porosity measurements of the imaged samples. Distributions in reactive surface area for each mineral phase were constructed by calculating surface areas in thousands of randomly selected subvolume images of the total sample, each normalized to the pore volume in that image. In all samples, there is little correlation between the reactive surface area fraction and the volumetric fraction of a mineral in a bulk rock. Berea sandstone was far less heterogeneous and has a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. In carbonates, heterogeneity is more complex and surface area must be characterized at multiple length scales for an accurate description of reactive transport. [1] Maher, Steefel, Depaolo and Vianni (2006) Geochimica et Cosmochimica Acta, 70, 337-363 [2] Landrot, Ajo-Franklin, Yang, Cabrini and Steefel (2012) Chemical Geology 318-319, 113-125 [3] Li, Peters and Celia (2007) American Journal of Science 307, 1146

  8. Size distribution of detached drops

    NASA Astrophysics Data System (ADS)

    Baluev, V. V.; Stepanov, V. M.

    1989-10-01

    The law governing the size distribution of detached gas-liquid streams of drops has been determined analytically, and a comparison is carried out against experimental data existing in the literature. The derived theoretical relationships offer an excellent description of existing experimental results.

  9. Size distribution of ring polymers

    NASA Astrophysics Data System (ADS)

    Medalion, Shlomi; Aghion, Erez; Meirovitch, Hagai; Barkai, Eli; Kessler, David A.

    2016-06-01

    We present an exact solution for the distribution of sample averaged monomer to monomer distance of ring polymers. For non-interacting and local-interaction models these distributions correspond to the distribution of the area under the reflected Bessel bridge and the Bessel excursion respectively, and are shown to be identical in dimension d ≥ 2, albeit with pronounced finite size effects at the critical dimension, d = 2. A symmetry of the problem reveals that dimension d and 4 ‑ d are equivalent, thus the celebrated Airy distribution describing the areal distribution of the d = 1 Brownian excursion describes also a polymer in three dimensions. For a self-avoiding polymer in dimension d we find numerically that the fluctuations of the scaled averaged distance are nearly identical in dimension d = 2, 3 and are well described to a first approximation by the non-interacting excursion model in dimension 5.

  10. Protein attachment to nanoporous anodic alumina for biotechnological applications: influence of pore size, protein size and functionalization path.

    PubMed

    Baranowska, Malgorzata; Slota, Agata J; Eravuchira, Pinkie J; Macias, Gerard; Xifré-Pérez, Elisabet; Pallares, Josep; Ferré-Borrull, Josep; Marsal, Lluís F

    2014-10-01

    Nanoporous anodic alumina (NAA) is a material with great interest in nanotechnology and with promising applications to biotechnology. Obtaining specific and regularly functionalized NAA surfaces is essential to obtain meaningful results and applications. Silane-PEG-NHS (triethoxysilane-polyethylene-glycol-N-hydroxysuccinimide) is a covalent linker commonly used for single-molecule studies. We investigate the functionalization of NAA with silane-PEG-NHS and compared with two common, but not single-molecule, grafting agents, APTMS (3-aminopropylotrimethoxysilane) as an electrostatic linker, and APTMS-GTA (3-aminopropylotrimethoxysilane-glutaraldehyde) as covalent. Another outcome of this study is to show how two proteins (collagen and bovine serum albumin, BSA) with different properties differentially arrange for different functionalizations and NAA pore sizes. FTIR is used to demonstrate the surface modification steps and fluorescence confocal microscopy reveals that silane-PEG-NHS results in a more homogeneous protein distribution in comparison to the other linkers. Reflection interference Fourier transform spectroscopy confirms the confocal fluorescence microscopy results and permits to estimate the amounts of linker and linked proteins within the pores. These results permit to obtain uniformly chemical modified NAA supports with a great value in biosensing, drug delivery and cell biology. PMID:25086305

  11. Direct measurement of the critical pore size in a polymer membrane

    NASA Astrophysics Data System (ADS)

    Ilton, Mark; Dimaria, Christian; Dalnoki-Veress, Kari

    The formation of pores is an important process in cellular membranes. Here we use freestanding polymer films as model membranes to study the stability of nucleated pores. Polymer membranes with pores of varying size are patterned using a lithographic technique. The membranes are heated above their glass transition temperature to allow viscous flow to occur. Pores with a radius larger than a critical value grow, while pores smaller than the critical radius are observed to shrink and eventually close. Remarkably, holes that are close enough to the critical radius neither grow nor shrink, even though the film is in the melt state. A simple model which takes into account the energy cost of having additional surface area at the edge of a pore describes the experiments with no free parameters. Biological membranes have an additional energetic cost of forming a pore, which we mimic using a lamellar-forming diblock copolymer. Indeed, we find that the critical pore radius is increased when pore formation is frustrated by molecular architecture.

  12. Relation between pore size and the compressibility of a confined fluid

    NASA Astrophysics Data System (ADS)

    Gor, Gennady Y.; Siderius, Daniel W.; Rasmussen, Christopher J.; Krekelberg, William P.; Shen, Vincent K.; Bernstein, Noam

    2015-11-01

    When a fluid is confined to a nanopore, its thermodynamic properties differ from the properties of a bulk fluid, so measuring such properties of the confined fluid can provide information about the pore sizes. Here, we report a simple relation between the pore size and isothermal compressibility of argon confined in such pores. Compressibility is calculated from the fluctuations of the number of particles in the grand canonical ensemble using two different simulation techniques: conventional grand-canonical Monte Carlo and grand-canonical ensemble transition-matrix Monte Carlo. Our results provide a theoretical framework for extracting the information on the pore sizes of fluid-saturated samples by measuring the compressibility from ultrasonic experiments.

  13. Relation between pore size and the compressibility of a confined fluid

    SciTech Connect

    Gor, Gennady Y.; Siderius, Daniel W.; Krekelberg, William P.; Shen, Vincent K.; Rasmussen, Christopher J.; Bernstein, Noam

    2015-11-21

    When a fluid is confined to a nanopore, its thermodynamic properties differ from the properties of a bulk fluid, so measuring such properties of the confined fluid can provide information about the pore sizes. Here, we report a simple relation between the pore size and isothermal compressibility of argon confined in such pores. Compressibility is calculated from the fluctuations of the number of particles in the grand canonical ensemble using two different simulation techniques: conventional grand-canonical Monte Carlo and grand-canonical ensemble transition-matrix Monte Carlo. Our results provide a theoretical framework for extracting the information on the pore sizes of fluid-saturated samples by measuring the compressibility from ultrasonic experiments.

  14. Pores Formed by Baxα5 Relax to a Smaller Size and Keep at Equilibrium

    PubMed Central

    Fuertes, Gustavo; García-Sáez, Ana J.; Esteban-Martín, Santi; Giménez, Diana; Sánchez-Muñoz, Orlando L.; Schwille, Petra; Salgado, Jesús

    2010-01-01

    Pores made by amphipathic cationic peptides (e.g., antimicrobials and fragments of pore-forming proteins) are typically studied by examining the kinetics of vesicle leakage after peptide addition or obtaining structural measurements in reconstituted peptide-lipid systems. In the first case, the pores have been considered transient phenomena that allow the relaxation of the peptide-membrane system. In the second, they correspond to equilibrium structures at minimum free energy. Here we reconcile both approaches by investigating the pore activity of the α5 fragment from the proapoptotic protein Bax (Baxα5) before and after equilibrium of peptide/vesicle complexes. Quenching assays on suspensions of large unilamellar vesicles suggest that in the presence of Baxα5, the vesicles maintain a leaky state for hours under equilibrium conditions. We proved and analyzed stable pores on single giant unilamellar vesicles (GUVs) in detail by monitoring the entrance of dyes added at different times after incubation with the peptide. When the GUVs came in contact with Baxα5, leakage started stochastically, was delayed for various periods of time, and in the majority of cases proceeded rapidly to completion. After hours in the presence of the peptide, the same individual GUVs that refilled completely at first instance maintained a porated state, which could be observed in subsequent leak-in events for serially added dyes. However, these long-term pores were smaller in size than the initial equilibration pores. Stable pores were also detected in GUVs made in the presence of Baxα5. The latter pores can be considered equilibrium states and may correspond to structures measured previously in bilayer stacks. Although pore formation may occur as a kinetic process, equilibrium pores may also be functionally relevant structures, especially in highly regulated systems such as the apoptotic mitochondrial pores induced by Bax. PMID:21044589

  15. Effect of large pore size of multifunctional mesoporous microsphere on removal of heavy metal ions.

    PubMed

    Yuan, Qing; Li, Nan; Chi, Yue; Geng, Wangchang; Yan, Wenfu; Zhao, Ying; Li, Xiaotian; Dong, Bin

    2013-06-15

    Pore size of mesoporous materials is crucial for their surface grafting. This article develops a novel multifunctional microsphere with a large pore size mesoporous silica shell (ca. 10.3 nm) and a magnetic core (Fe₃O₄), which is fabricated using cetyltrimethylammonium bromide (CTAB) as pore-forming agents, tetraethyl orthosilicate (TEOS) as silicon source through a sol-gel process. Compared with small pore size mesoporous silica magnetic microspheres (ca. 2-4 nm), the large pore size one can graft 447 mg/g amino groups in order to adsorb more heavy metal ions (Pb(2+): 880.6 mg/g, Cu(2+): 628.3mg/g, Cd(2+): 492.4 mg/g). The metal-loaded multifunctional microspheres could be easily removed from aqueous solution by magnetic separation and regenerated easily by acid treatment. The results suggest that the large pore size multifunctional microspheres are potentially useful materials for high effectively adsorbing and removing different heavy metal ions in aqueous solution. PMID:23618656

  16. Seismic signatures of reservoir transport properties and pore fluid distribution

    SciTech Connect

    Akbar, N. ); Mavko, G.; Nur, A.; Dvorkin, J. . Dept. of Geophysics)

    1994-08-01

    The authors investigate the effects of permeability, frequency, and fluid distribution on the viscoelastic behavior of rock. The viscoelastic response of rock to seismic waves depends on the relative motion of pore fluid with respect to the solid phase. They consider wave-induced squirt fluid flow at two scales: (1) local microscopic flow at the smallest scale of saturation heterogeneity (e.g., within a single pore) and (2) macroscopic flow at a larger scale of fluid-saturated and dry patches. They explore the circumstances under which each of these mechanisms prevails. They examine such flows under the conditions of uniform confining (bulk) compression and obtain the effective dynamic bulk modulus of rock. The solutions are formulated in terms of generalized frequencies that depend on frequency, saturation, fluid and gas properties, and on the macroscopic properties of rock such as permeability, porosity, and dry bulk modulus. The study includes the whole range of saturation and frequency; therefore, the authors provide the missing link between the low-frequency limit and the high-frequency limit given by Mavko and Jizba. Further, they compare their model with Biot's theory and introduce a geometrical factor whose numeric value gives an indication as to whether local fluid squirt or global mechanisms dominate the viscoelastic properties of porous materials. The important results of their theoretical modeling are: (1) a hysteresis of acoustic velocity versus saturation resulting from variations in fluid distributions, and (2) two peaks of acoustic wave attenuation--one at low frequency and another at higher frequency (caused by local flow). Both theoretical results are compared with experimental data.

  17. Synthesis of mesoporous carbon nanoparticles with large and tunable pore sizes

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Yu, Meihua; Li, Yang; Li, Jiansheng; Wang, Jing; Yu, Chengzhong; Wang, Lianjun

    2015-07-01

    Mesoporous carbon nanoparticles (MCNs) with large and adjustable pores have been synthesized by using poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a template and resorcinol-formaldehyde (RF) as a carbon precursor. The resulting MCNs possess small diameters (100-126 nm) and high BET surface areas (up to 646 m2 g-1). By using home-designed block copolymers, the pore size of MCNs can be tuned in the range of 13-32 nm. Importantly, the pore size of 32 nm is the largest among the MCNs prepared by the soft-templating route. The formation mechanism and structure evolution of MCNs were studied by TEM and DLS measurements, based on which a soft-templating/sphere packing mechanism was proposed. Because of the large pores and small particle sizes, the resulting MCNs were excellent nano-carriers to deliver biomolecules into cancer cells. MCNs were further demonstrated with negligible toxicity. It is anticipated that this carbon material with large pores and small particle sizes may have excellent potential in drug/gene delivery.Mesoporous carbon nanoparticles (MCNs) with large and adjustable pores have been synthesized by using poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a template and resorcinol-formaldehyde (RF) as a carbon precursor. The resulting MCNs possess small diameters (100-126 nm) and high BET surface areas (up to 646 m2 g-1). By using home-designed block copolymers, the pore size of MCNs can be tuned in the range of 13-32 nm. Importantly, the pore size of 32 nm is the largest among the MCNs prepared by the soft-templating route. The formation mechanism and structure evolution of MCNs were studied by TEM and DLS measurements, based on which a soft-templating/sphere packing mechanism was proposed. Because of the large pores and small particle sizes, the resulting MCNs were excellent nano-carriers to deliver biomolecules into cancer cells. MCNs were further demonstrated with negligible toxicity. It is anticipated that this carbon material with large pores and

  18. Passive permeability and effective pore size of HeLa cell nuclear membranes.

    PubMed

    Samudram, Arunkarthick; Mangalassery, Bijeesh M; Kowshik, Meenal; Patincharath, Nandakumar; Varier, Geetha K

    2016-09-01

    Nuclear pore complexes in the nuclear membrane act as the sole gateway of transport of molecules from the cytoplasm to the nucleus and vice versa. Studies on biomolecular transport through nuclear membranes provide vital data on the nuclear pore complexes. In this work, we use fluorescein isothiocyanate-labeled dextran molecules as a model system and study the passive nuclear import of biomolecules through nuclear pore complexes in digitonin-permeabilized HeLa cells. Experiments are carried out under transient conditions in the time lapse imaging scheme using an in-house constructed confocal laser scanning microscope. Transport rates of dextran molecules having molecular weights of 4-70 kDa corresponding to Stokes radius of 1.4-6 nm are determined. Analyzing the permeability of the nuclear membrane for different sizes the effective pore radius of HeLa cell nuclear membrane is determined to be 5.3 nm, much larger than the value reported earlier using proteins as probe molecules. The range of values reported for the nuclear pore radius suggest that they may not be rigid structures and it is quite probable that the effective pore size of nuclear pore complexes is critically dependent on the probe molecules and on the environmental factors. PMID:27338984

  19. The influence of porous medium characteristics and measurement scale on pore-scale distributions of residual nonaqueous-phase liquids

    NASA Astrophysics Data System (ADS)

    Mayer, Alex S.; Miller, Cass T.

    1992-11-01

    A series of experiments was performed to characterize the morphologic distribution of nonaqueous-phase liquids (NAPL's) at residual saturation, as a function of porous medium size. Morphologic characterization of NAPL distributions was accomplished using a novel in situ polymerization technique. The porous medium consisted of glass beads. Blob length, volume and shape characteristics were determined for each experiment, and pore size distributions were determined through capillary pressure-saturation experiments. Both the blob lenght and pore size distributions were fitted to a van Genuchten function. Both blob lenght and pressure-saturation data could be scaled with the same averaged porous medium characteristics. The blob length distributions were found to be wider than the pore size distributions. Estimates of representative elementary volumes (REV's) were generated from statistical analysis using a van Genuchten cumulative frequency distribution function for blob lenght and an empirical function for blob volume as a function of blob length. Simulations were also performed using a Monte Carlo method. The size of the REV needed for a given level of prediction of the residual saturation level was found to increase as a function of mean particle volume for the similar used in this study. Extrapolation of the REV analysis suggests that the size of an REV will increase rapidly as uniformity of the medium decreases. If this extrapolation holds true, significant uncertainty would exist in most determination of residual saturation for poorly sorted media that have been reported to date.

  20. Oxidation of activated carbon fibers: Effect on pore size, surface chemistry, and adsorption properties

    SciTech Connect

    Mangun, C.L.; Benak, K.R.; Daley, M.A.; Economy, J.

    1999-12-01

    Activated carbon fibers (ACFs) were oxidized using both aqueous and nonaqueous treatments. As much as 29 wt% oxygen can be incorporated onto the pore surface in the form of phenolic hydroxyl, quinine, and carboxylic acid groups. The effect of oxidation on the pore size, pore volume, and the pore surface chemistry was thoroughly examined. The average micropore size is typically affected very little by aqueous oxidation while the micropore volume and surface area decreases with such a treatment. In contrast, the micropore size and micropore volume both increase with oxidation in air. Oxidation of the fibers produces surface chemistries in the pore that provide for enhanced adsorption of basic (ammonia) and polar (acetone) molecules at ambient and nonambient temperatures. The adsorption capacity of the oxidized fibers for acetone is modestly better than the untreated ACFs while the adsorption capacity for ammonia can increase up to 30 times compared to untreated ACFs. The pore surface chemical makeup was analyzed using elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS).

  1. Size distribution of ring polymers

    PubMed Central

    Medalion, Shlomi; Aghion, Erez; Meirovitch, Hagai; Barkai, Eli; Kessler, David A.

    2016-01-01

    We present an exact solution for the distribution of sample averaged monomer to monomer distance of ring polymers. For non-interacting and local-interaction models these distributions correspond to the distribution of the area under the reflected Bessel bridge and the Bessel excursion respectively, and are shown to be identical in dimension d ≥ 2, albeit with pronounced finite size effects at the critical dimension, d = 2. A symmetry of the problem reveals that dimension d and 4 − d are equivalent, thus the celebrated Airy distribution describing the areal distribution of the d = 1 Brownian excursion describes also a polymer in three dimensions. For a self-avoiding polymer in dimension d we find numerically that the fluctuations of the scaled averaged distance are nearly identical in dimension d = 2, 3 and are well described to a first approximation by the non-interacting excursion model in dimension 5. PMID:27302596

  2. Size distribution of ring polymers.

    PubMed

    Medalion, Shlomi; Aghion, Erez; Meirovitch, Hagai; Barkai, Eli; Kessler, David A

    2016-01-01

    We present an exact solution for the distribution of sample averaged monomer to monomer distance of ring polymers. For non-interacting and local-interaction models these distributions correspond to the distribution of the area under the reflected Bessel bridge and the Bessel excursion respectively, and are shown to be identical in dimension d ≥ 2, albeit with pronounced finite size effects at the critical dimension, d = 2. A symmetry of the problem reveals that dimension d and 4 - d are equivalent, thus the celebrated Airy distribution describing the areal distribution of the d = 1 Brownian excursion describes also a polymer in three dimensions. For a self-avoiding polymer in dimension d we find numerically that the fluctuations of the scaled averaged distance are nearly identical in dimension d = 2, 3 and are well described to a first approximation by the non-interacting excursion model in dimension 5. PMID:27302596

  3. Pore size assessment during corneal endothelial cells permeabilization by femtosecond laser activated carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Jumelle, C.; Mauclair, C.; Houzet, J.; Bernard, A.; He, Z.; Piselli, S.; Perrache, C.; Egaud, G.; Baubeau, E.; Gain, P.; Thuret, G.

    2015-07-01

    Corneal therapeutic molecules delivery represents a promising solution to maintain human corneal endothelial cells (HCECs) viability, but the difficulty is transport across cell membrane. A new delivery method published recently consists in ephemerally permeabilizing cell membranes using a photo-acoustic reaction produced by carbon nanoparticles (CNPs) and femtosecond laser (FsL). The aim of this work is to investigate the size of pores formed at cell membrane by this technique. To induce cell permeabilization, HCECs were put in contact with CNPs and irradiated with a 500 μm diameter Ti:Sa FsL focalized spot. Four sizes of marker molecules were delivered into HCECs to investigate pore sizes: calcein (1.2 nm), FITC-Dextran 4kDa (2.8 nm) and FITC-Dextran 70kDa (12 nm) and FITC-Dextran 2MDa (50 nm). Delivery of each molecule was assessed by flow cytometry, a technique able to measure their presence into cells. We showed that the delivery rate was dependent of their size. Calcein was delivered in 56.1±8.2% of HCECs, FITC-Dextran 4kDa in 42.2±3.5%, FITC-Dextran 70 kDa in 21.5±2.7% and finally FITC-Dextran 2MDa in 12.9±2.0%. It means that a large number of pores in the size ranging from 1.2 to 2.8 nm were formed. However, 12 nm and larger pores were almost half more infrequent. Pore sizes formed at cell membrane by the technique of cell permeabilization by FsL activated CNPs was investigated. The results indicated that the pore sizes are large enough for the efficient delivery of small, medium and big therapeutics molecules on HCECs by this technique.

  4. Tricontinuous Cubic Nanostructure and Pore Size Patterning in Mesostructured Silica Films Templated with Glycerol Monooleate

    PubMed Central

    Dunphy, Darren R.; Garcia, Fred L.; Kaehr, Bryan; Khripin, Constantine Y.; Collord, Andrew D.; Baca, Helen K.; Tate, Michael P.; Hillhouse, Hugh W.; Strzalka, Joseph W.; Jiang, Zhang; Wang, Jin; Brinker, C. Jeffrey

    2011-01-01

    The fabrication of nanostructured films possessing tricontinuous minimal surface mesophases with well-defined framework and pore connectivity remains a difficult task. As a new route to these structures, we introduce glycerol monooleate (GMO) as a template for evaporation-induced self-assembly. As deposited, a nanostructured double gyroid phase is formed, as indicated by analysis of grazing-incidence small-angle x-ray scattering data. Removal of GMO by UV/O3 treatment or acid extraction induces a phase change to a nanoporous body-centered structure which we tentatively identify as based on the IW-P surface. To improve film quality, we add a co-surfactant to the GMO in a mass ratio of 1:10; when this co-surfactant is cetyltrimethylammonium bromide, we find an unusually large pore size (8-12 nm) in acid extracted films, while UV/O3 treated films yield pores of only ca. 4 nm. Using this pore size dependence on film processing procedure, we create a simple method for patterning pore size in nanoporous films, demonstrating spatially-defined size-selective molecular adsorption. PMID:21572556

  5. Hemoglobin precipitation by polyethylene glycols leads to underestimation of membrane pore sizes.

    PubMed

    Quijano, Jairo C; Lemeshko, Victor V

    2008-12-01

    The size of pores formed in the plasma membrane by various substances is frequently determined using polyethylene glycols as osmotic protectants. In this work, we have found that the size of pores formed by saponin in the red blood cell membrane determined by hemolysis versus molecular weight of polyethylene glycol was different to that estimated by light dispersion of cell suspensions. After complete swelling of cells induced by saponin in semiisotonic salt media containing 150 mOsm PEG-4000 or PEG-3000, a significant increase in the light absorbance at 640 nm was developed resulting from the formation of hemoglobin precipitates. Easily sedimenting aggregates were also formed when the supernatant of lysed cells was added to the equiosmotic solutions of polyethylene glycols with molecular weight higher than 1000. We suggest that the real size of large pores could be underestimated due to the phenomenon of hemoglobin precipitation by polyethylene glycols. PMID:18692020

  6. Characterizing pore sizes and water structure in stimuli-responsive hydrogels

    SciTech Connect

    Hoffman, A.S.; Antonsen, K.P.; Ashida, T.; Bohnert, J.L.; Dong, L.C.; Nabeshima, Y.; Nagamatsu, S.; Park, T.G.; Sheu, M.S.; Wu, X.S.; Yan, Q.

    1993-12-31

    Hydrogels have been extensively investigated as potential matrices for drug delivery. In particular, hydrogels responsive to pH and temperature changes have been of greatest interest most recently. Proteins and peptide drugs are especially relevant for delivery from such hydrogel matrices due to the relatively {open_quotes}passive{close_quotes} and biocompatible microenvironment which should exist within the hydrogel aqueous pores. The large molecular size of many proteins requires an interconnected large pore structure. Furthermore, the gel pore {open_quotes}walls{close_quotes} should not provide hydrophobic sites for strong interactions with proteins. In the special case of ion exchange release the protein would be attracted by opposite charges on the polymer backbones. Therefore, it is important both to control and to characterize the pore structure and the water character within a hydrogel to be used or protein or peptide drug delivery. This talk will critically review techniques for estimating these two key parameters in hydrogels.

  7. Pore Size Control of Ultra-thin Silicon Membranes by Rapid Thermal Carbonization

    PubMed Central

    Fang, David Z.; Striemer, Christopher C.; Gaborski, Thomas R.; McGrath, James L.; Fauchet, Philippe M.

    2010-01-01

    Rapid thermal carbonization in a dilute acetylene (C2H2) atmosphere has been used to chemically modify and precisely tune the pore size of ultrathin porous nanocrystalline silicon (pnc-Si). The magnitude of size reduction was controlled by varying the process temperature and time. Under certain conditions, the carbon coating displayed atomic ordering indicative of graphene layer formation conformal to the pore walls. Initial experiments show that carbonized membranes follow theoretical predictions for hydraulic permeability and retain the precise separation capabilities of untreated membranes. PMID:20839831

  8. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    NASA Astrophysics Data System (ADS)

    Diallo, S. O.

    2015-07-01

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (˜12 and 18 Å, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. This suppression is accompanied by a systematic dependence of the average translational diffusion coefficient Dr and relaxation time <τ0> of the restricted water on pore size and temperature. The observed Dr values are tested against a proposed scaling law, in which the translational diffusion coefficient Dr of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient Dc associated with the water bound to the pore walls and the ratio θ of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  9. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    SciTech Connect

    Diallo, S. O.

    2015-07-16

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (similar to 12 and 18 angstrom, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation time [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio theta of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  10. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    DOE PAGESBeta

    Diallo, S. O.

    2015-07-16

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (similar to 12 and 18 angstrom, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation timemore » [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio theta of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.« less

  11. Simple thermal treatment for the size control of pore arrays in a polystyrene colloidal crystal films

    NASA Astrophysics Data System (ADS)

    Jamiolkowski, Ryan M.; Fiorenza, Shane A.; Chen, Kevin; Tate, Alyssa M.; Pfeil, Shawn H.; Goldman, Yale E.

    Nanosphere Lithography (NSL) offers an attractive route to fabricating periodic structures with nanoscale features, without e-beam or deep UV lithography. In particular, it is uniquely suited to the low cost fabrication of large repeated arrays pores or pillars created by taking advantage of the interstitial spaces in close-packed monolayers of nano to micro-scale beads. However pore size, shape, and spacing cannot be controlled independently. We present both a robust method for producing large, approximately 1 cm2, hexagonally close packed monolayer films of 1 micron diameter polystyrene beads on glass substrates, and thermal treatment of these films near the glass temperature, Tg, of polystyrene to modify the pore size. This builds on earlier work showing that pore size can be modified for colloidal crystals formed at a liquid gas interface [2]. These processes promise a simple, reproducible, and low cost route to periodic pore arrays for nano-photonic applications such as zero mode waveguides (ZMWs) Funding: F30 AI114187 (RMJ), R01-GM080376 (YEG).

  12. Self-supporting nanopore membranes with controlled pore size and shape.

    PubMed

    Lu, Zhe-Xue; Namboodiri, Arya; Collinson, Maryanne M

    2008-05-01

    Self-supporting membranes containing either isolated or organized arrays of nanosized pores have been prepared using a nonlithographic approach by coupling sol-gel processing, thin film preparation, and templating. Specifically, polystyrene latex spheres were doped into a hybrid sol prepared from tetraethoxysilane and dimethyldiethoxysilane and the resultant sol spin cast on a sacrificial support. Upon removal of the template and the sacrificial support, the self-supporting nanopore membranes were transferred to glass for characterization by atomic force microscopy and scanning electron microscopy. Through variations in the thickness of the membranes and the size of the polystyrene latex spheres, the geometry (cylinder-like to asymmetric-like) and the dimensions of the nanopores were altered. Pores with diameters that range from 35 to 2100 nm, aspect ratios (defined as the top pore diameter divided by the bottom pore diameter) from 1-4, and depths (effective film thickness) from 50 to 1500 nms have been prepared using templates that range in diameter from 100 to 3100 nm. The method described employs "wet-chemistry", is highly versatile, and is easily amenable to modification by utilizing templates of different sizes and geometries to create stable membranes with different pore geometries and sizes that can be used as platforms for nanofiltration and/or chemical sensors. PMID:19206497

  13. Development of gelatin-chitosan-hydroxyapatite based bioactive bone scaffold with controlled pore size and mechanical strength.

    PubMed

    Maji, Kanchan; Dasgupta, Sudip; Kundu, Biswanath; Bissoyi, Akalabya

    2015-01-01

    Hydroxyapatite-chitosan/gelatin (HA:Chi:Gel) nanocomposite scaffold has potential to serve as a template matrix to regenerate extra cellular matrix of human bone. Scaffolds with varying composition of hydroxyapatite, chitosan, and gelatin were prepared using lyophilization technique where glutaraldehyde (GTA) acted as a cross-linking agent for biopolymers. First, phase pure hydroxyapatite-chitosan nanocrystals were in situ synthesized by coprecipitation method using a solution of 2% acetic acid dissolved chitosan and aqueous solution of calcium nitrate tetrahydrate [Ca(NO3)2,4H2O] and diammonium hydrogen phosphate [(NH4)2H PO4]. Keeping solid loading constant at 30 wt% and changing the composition of the original slurry of gelatin, HA-chitosan allowed control of the pore size, its distribution, and mechanical properties of the scaffolds. Microstructural investigation by scanning electron microscopy revealed the formation of a well interconnected porous scaffold with a pore size in the range of 35-150 μm. The HA granules were uniformly dispersed in the gelatin-chitosan network. An optimal composition in terms of pore size and mechanical properties was obtained from the scaffold with an HA:Chi:Gel ratio of 21:49:30. The composite scaffold having 70% porosity with pore size distribution of 35-150 μm exhibited a compressive strength of 3.3-3.5 MPa, which is within the range of that exhibited by cancellous bone. The bioactivity of the scaffold was evaluated after conducting mesenchymal stem cell (MSC) - materials interaction and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay using MSCs. The scaffold found to be conducive to MSC's adhesion as evident from lamellipodia, filopodia extensions from cell cytoskeleton, proliferation, and differentiation up to 14 days of cell culture. PMID:26335156

  14. Pore size regulates operating stomatal conductance, while stomatal densities drive the partitioning of conductance between leaf sides

    PubMed Central

    Fanourakis, Dimitrios; Giday, Habtamu; Milla, Rubén; Pieruschka, Roland; Kjaer, Katrine H.; Bolger, Marie; Vasilevski, Aleksandar; Nunes-Nesi, Adriano; Fiorani, Fabio; Ottosen, Carl-Otto

    2015-01-01

    Background and Aims Leaf gas exchange is influenced by stomatal size, density, distribution between the leaf adaxial and abaxial sides, as well as by pore dimensions. This study aims to quantify which of these traits mainly underlie genetic differences in operating stomatal conductance (gs) and addresses possible links between anatomical traits and regulation of pore width. Methods Stomatal responsiveness to desiccation, gs-related anatomical traits of each leaf side and estimated gs (based on these traits) were determined for 54 introgression lines (ILs) generated by introgressing segments of Solanum pennelli into the S. lycopersicum ‘M82’. A quantitative trait locus (QTL) analysis for stomatal traits was also performed. Key Results A wide genetic variation in stomatal responsiveness to desiccation was observed, a large part of which was explained by stomatal length. Operating gs ranged over a factor of five between ILs. The pore area per stomatal area varied 8-fold among ILs (2–16 %), and was the main determinant of differences in operating gs between ILs. Operating gs was primarily positioned on the abaxial surface (60–83 %), due to higher abaxial stomatal density and, secondarily, to larger abaxial pore area. An analysis revealed 64 QTLs for stomatal traits in the ILs, most of which were in the direction of S. pennellii. Conclusions The data indicate that operating and maximum gs of non-stressed leaves maintained under stable conditions deviate considerably (by 45–91 %), because stomatal size inadequately reflects operating pore area (R2 = 0·46). Furthermore, it was found that variation between ILs in both stomatal sensitivity to desiccation and operating gs is associated with features of individual stoma. In contrast, genotypic variation in gs partitioning depends on the distribution of stomata between the leaf adaxial and abaxial epidermis. PMID:25538116

  15. Size Control of Porous Silicon-Based Nanoparticles via Pore-Wall Thinning.

    PubMed

    Secret, Emilie; Leonard, Camille; Kelly, Stefan J; Uhl, Amanda; Cozzan, Clayton; Andrew, Jennifer S

    2016-02-01

    Photoluminescent silicon nanocrystals are very attractive for biomedical and electronic applications. Here a new process is presented to synthesize photoluminescent silicon nanocrystals with diameters smaller than 6 nm from a porous silicon template. These nanoparticles are formed using a pore-wall thinning approach, where the as-etched porous silicon layer is partially oxidized to silica, which is dissolved by a hydrofluoric acid solution, decreasing the pore-wall thickness. This decrease in pore-wall thickness leads to a corresponding decrease in the size of the nanocrystals that make up the pore walls, resulting in the formation of smaller nanoparticles during sonication of the porous silicon. Particle diameters were measured using dynamic light scattering, and these values were compared with the nanocrystallite size within the pore wall as determined from X-ray diffraction. Additionally, an increase in the quantum confinement effect is observed for these particles through an increase in the photoluminescence intensity of the nanoparticles compared with the as-etched nanoparticles, without the need for a further activation step by oxidation after synthesis. PMID:26796986

  16. Vesicular release of neurotransmitters: converting amperometric measurements into size, dynamics and energetics of initial fusion pores.

    PubMed

    Oleinick, Alexander; Lemaître, Frédéric; Collignon, Manon Guille; Svir, Irina; Amatore, Christian

    2013-01-01

    Amperometric currents displaying a pre-spike feature (PSF) may be treated so as to lead to precise information about initial fusion pores, viz., about the crucial event initiating neurotransmitter vesicular release in neurons and medullary glands. However, amperometric data alone are not self-sufficient, so their full exploitation requires external calibration to solve the inverse problem. For this purpose we resorted to patch-clamp measurements published in the literature on chromaffin cells. Reported pore radii were thus used to evaluate the diffusion rate of neurotransmitter cations in the partially altered matrix located near the fusion pore entrance. This allowed an independent determination of each initial fusion pore radius giving rise to a single PSF event. The statistical distribution of the radii thus obtained provided for the first time an experimental access to the potential energy well governing the thermodynamics of such systems. The shape of the corresponding potential energy well strongly suggested that, after their creation, initial fusion pores are essentially controlled by the usual physicochemical laws describing pores formed in bilayer lipidic biological membranes, i.e., they have an essentially lipidic nature. PMID:24466657

  17. Metal electrode integration on macroporous silicon: pore distribution and morphology

    NASA Astrophysics Data System (ADS)

    Scheen, Gilles; Bassu, Margherita; Francis, Laurent A.

    2012-07-01

    In this work, a new approach for the one-step integration of interdigitated electrodes on macroporous silicon substrates is presented. Titanium/gold interdigitated electrodes are used to pattern p-type silicon substrates prior the anodization in an organic electrolyte. The electrolyte characteristics, conductivity, and pH have been found to affect the adherence of the metal layer on the silicon surface during the electrochemical etching. The impact of the metal pattern on size distribution and morphology of the resulting macroporous silicon layer is analyzed. A formation mechanism supported by finite element simulation is proposed.

  18. Metal electrode integration on macroporous silicon: pore distribution and morphology

    PubMed Central

    2012-01-01

    In this work, a new approach for the one-step integration of interdigitated electrodes on macroporous silicon substrates is presented. Titanium/gold interdigitated electrodes are used to pattern p-type silicon substrates prior the anodization in an organic electrolyte. The electrolyte characteristics, conductivity, and pH have been found to affect the adherence of the metal layer on the silicon surface during the electrochemical etching. The impact of the metal pattern on size distribution and morphology of the resulting macroporous silicon layer is analyzed. A formation mechanism supported by finite element simulation is proposed. PMID:22799456

  19. Pore scale heterogeneity in the mineral distribution and surface area of porous rocks

    NASA Astrophysics Data System (ADS)

    Lai, Peter; Moulton, Kevin; Krevor, Samuel

    2014-05-01

    There are long-standing challenges in characterizing reactive transport in porous media at scales larger than individual pores. This hampers the prediction of the field-scale impact of geochemical processes on fluid flow [1]. This is a source of uncertainty for carbon dioxide injection, which results in a reactive fluid-rock system, particularly in carbonate rock reservoirs. A potential cause is the inability of the continuum approach to incorporate the impact of heterogeneity in pore-scale reaction rates. This results in part from pore-scale heterogeneities in surface area of reactive minerals [2,3]. The objective of this study was to quantify heterogeneity in reactive surface and observe the extent of its non-normal character. In this study we describe our work in using micron-scale x-ray imaging and other spectroscopic techniques for the purpose of describing the statistical distribution of reactive surface area within a porous medium, and identifying specific mineral phases and their distribution in 3-dimensions. Using in-house image processing techniques and auxilary charactersation with thin section, electron microscope and spectroscopic techniques we quantified the surface area of each mineral phase in the x-ray CT images. This quantification was validated against nitrogen BET surface area and backscattered electron imaging measurements of the CT-imaged samples. Distributions in reactive surface area for each mineral phase were constructed by calculating surface areas in thousands of randomly selected subvolume images of the total sample, each normalized to the pore volume in that image. In all samples, there is little correlation between the reactive surface area fraction and the volumetric fraction of a mineral in a bulk rock. Berea sandstone was far less heterogeneous and has a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. In carbonates, heterogeneity is more complex and surface area must be

  20. Three-Dimensional Scaffolds for Tissue Engineering Applications: Role of Porosity and Pore Size

    PubMed Central

    Loh, Qiu Li

    2013-01-01

    Tissue engineering applications commonly encompass the use of three-dimensional (3D) scaffolds to provide a suitable microenvironment for the incorporation of cells or growth factors to regenerate damaged tissues or organs. These scaffolds serve to mimic the actual in vivo microenvironment where cells interact and behave according to the mechanical cues obtained from the surrounding 3D environment. Hence, the material properties of the scaffolds are vital in determining cellular response and fate. These 3D scaffolds are generally highly porous with interconnected pore networks to facilitate nutrient and oxygen diffusion and waste removal. This review focuses on the various fabrication techniques (e.g., conventional and rapid prototyping methods) that have been employed to fabricate 3D scaffolds of different pore sizes and porosity. The different pore size and porosity measurement methods will also be discussed. Scaffolds with graded porosity have also been studied for their ability to better represent the actual in vivo situation where cells are exposed to layers of different tissues with varying properties. In addition, the ability of pore size and porosity of scaffolds to direct cellular responses and alter the mechanical properties of scaffolds will be reviewed, followed by a look at nature's own scaffold, the extracellular matrix. Overall, the limitations of current scaffold fabrication approaches for tissue engineering applications and some novel and promising alternatives will be highlighted. PMID:23672709

  1. Fabrication of Cell-Laden Macroporous Biodegradable Hydrogels with Tunable Porosities and Pore Sizes

    PubMed Central

    Wang, Limin; Lu, Steven; Lam, Johnny; Kasper, F. Kurtis

    2015-01-01

    In this work, we investigated a cytocompatible particulate leaching method for the fabrication of cell-laden macroporous hydrogels. We used dehydrated and uncrosslinked gelatin microspheres as leachable porogens to create macroporous oligo(poly(ethylene glycol) fumarate) hydrogels. Varying gelatin content and size resulted in a wide range of porosities and pore sizes, respectively. Encapsulated mesenchymal stem cells (MSCs) exhibited high viability immediately following the fabrication process, and culture of cell-laden hydrogels revealed improved cell viability with increasing porosity. Additionally, the osteogenic potential of the encapsulated MSCs was evaluated over 16 days. Overall, this study presents a robust method for the preparation of cell-laden macroporous hydrogels with desired porosity and pore size for tissue engineering applications. PMID:25156274

  2. Effective porosity and pore-throat sizes of Conasauga Group mudrock: Application, test and evaluation of petrophysical techniques

    SciTech Connect

    Dorsch, J.; Katsube, T.J.; Sanford, W.E. |; Dugan, B.E.; Tourkow, L.M.

    1996-04-01

    Effective porosity (specifically referring to the interconnected pore space) was recently recognized as being essential in determining the effectiveness and extent of matrix diffusion as a transport mechanism within fractured low-permeability rock formations. The research presented in this report was performed to test the applicability of several petrophysical techniques for the determination of effective porosity of fine-grained siliciclastic rocks. In addition, the aim was to gather quantitative data on the effective porosity of Conasauga Group mudrock from the Oak Ridge Reservation (ORR). The quantitative data reported here include not only effective porosities based on diverse measurement techniques, but also data on the sizes of pore throats and their distribution, and specimen bulk and grain densities. The petrophysical techniques employed include the immersion-saturation method, mercury and helium porosimetry, and the radial diffusion-cell method.

  3. Pore Size Effect on Methane Adsorption in Mesoporous Silica Materials Studied by Small-Angle Neutron Scattering.

    PubMed

    Chiang, Wei-Shan; Fratini, Emiliano; Baglioni, Piero; Chen, Jin-Hong; Liu, Yun

    2016-09-01

    Methane adsorption in model mesoporous silica materials with the size range characteristic of shale is studied by small-angle neutron scattering (SANS). Size effect on the temperature-dependent gas adsorption at methane pressure about 100 kPa is investigated by SANS using MCM-41 and SBA-15 as adsorbents. Above the gas-liquid condensation temperature, the thickness of the adsorption layer is found to be roughly constant as a function of the temperature. Moreover, the gas adsorption properties, such as the adsorbed layer thickness and the specific amount of adsorbed gas, have little dependence on the pore size being studied, i.e., pore radius of 16.5 and 34.1 Å, but are mainly affected by the roughness of the pore surfaces. Hence, the surface properties of the pore wall are more dominant than the pore size in determining the methane gas adsorption of pores at the nanometer size range. Not surprisingly, the gas-liquid condensation temperature is observed to be sensitive to pore size and shifts to higher temperature when the pore size is smaller. Below the gas-liquid condensation temperature, even though the majority of gas adsorption experiments/simulations have assumed the density of confined liquid to be the same as the bulk density, the measured methane mass density in our samples is found to be appreciably smaller than the bulk methane density regardless of the pore sizes studied here. The mass density of liquid/solid methane in pores with different sizes shows different temperature dependence below the condensation temperature. With decreasing temperature, the methane density in larger pores (SBA-15) abruptly increases at approximately 65 K and then plateaus. In contrast, the density in smaller pores (MCM-41) monotonically increases with decreasing temperature before reaching a plateau at approximately 30 K. PMID:27512895

  4. Tuning Pore Size in Square-Lattice Coordination Networks for Size-Selective Sieving of CO2.

    PubMed

    Chen, Kai-Jie; Madden, David G; Pham, Tony; Forrest, Katherine A; Kumar, Amrit; Yang, Qing-Yuan; Xue, Wei; Space, Brian; Perry, John J; Zhang, Jie-Peng; Chen, Xiao-Ming; Zaworotko, Michael J

    2016-08-22

    Porous materials capable of selectively capturing CO2 from flue-gases or natural gas are of interest in terms of rising atmospheric CO2 levels and methane purification. Size-exclusive sieving of CO2 over CH4 and N2 has rarely been achieved. Herein we show that a crystal engineering approach to tuning of pore-size in a coordination network, [Cu(quinoline-5-carboxyate)2 ]n (Qc-5-Cu) ena+bles ultra-high selectivity for CO2 over N2 (SCN ≈40 000) and CH4 (SCM ≈3300). Qc-5-Cu-sql-β, a narrow pore polymorph of the square lattice (sql) coordination network Qc-5-Cu-sql-α, adsorbs CO2 while excluding both CH4 and N2 . Experimental measurements and molecular modeling validate and explain the performance. Qc-5-Cu-sql-β is stable to moisture and its separation performance is unaffected by humidity. PMID:27439315

  5. Imaging calcium carbonate distribution in human sweat pore in vivo using nonlinear microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Xueqin; Gasecka, Alicja; Formanek, Florian; Galey, Jean-Baptiste; Rigneault, Hervé

    2015-03-01

    Nonlinear microscopies, including two-photon excited autofluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS), were used to study individual human sweat pore morphology and topically applied antiperspirant salt penetration inside sweat pore, in vivo on human palms. Sweat pore inner morphology in vivo was imaged up to the depth of 100 μm by TPEF microscopy. The 3D penetration and distribution of "in situ calcium carbonate" (isCC), an antiperspirant salt model, was investigated using CARS microscopy.

  6. Strain-based in-situ study of anion and cation insertion into porous carbon electrodes with different pore sizes

    SciTech Connect

    Black, Jennifer M; Feng, Guang; Fulvio, Pasquale F; Hillesheim, Patrick C; Dai, Sheng; Gogotsi, Yury G.; Cummings, Peter T; Kalinin, Sergei V; Balke, Nina

    2013-01-01

    The expansion of porous carbon electrodes in a room temperature ionic liquid (RTIL) is studied using in-situ atomic force microscopy (AFM). The effect of carbon surface area and pore size/pore size distribution on the observed strain profile and ion kinetics is examined. Also, the influence of potential scan rate on the strain response is investigated. By analyzing the strain data at various potential scan rates information on ion kinetics in the different carbon materials is obtained. Molecular dynamics (MD) simulations are performed to compare with and provide molecular insights into experimental results, which is the first MD work investigating the pressure exerted on porous electrodes under applied potential in a RTIL electrolyte. Using MD, the pressure exerted on the pore wall is calculated as a function of potential/charge for both a micropore (1.2 nm) and a mesopore (7.0 nm). The shape of the calculated pressure profile matches closely with the strain profiles observed experimentally.

  7. Control of both particle and pore size in nanoporous palladium alloy powders

    SciTech Connect

    Jones, Christopher G.; Cappillino, Patrick J.; Stavila, Vitalie; Robinson, David B.

    2014-07-15

    Energy storage materials often involve chemical reactions with bulk solids. Porosity within the solids can enhance reaction rates. The porosity can be either within or between individual particles of the material. Greater control of the size and uniformity of both types of pore should lead to enhancements of charging and discharging rates in energy storage systems. Furthermore, to control both particle and pore size in nanoporous palladium (Pd)-based hydrogen storage materials, first we created uniformly sized copper particles of about 1 μm diameter by the reduction of copper sulfate with ascorbic acid. In turn, these were used as reducing agents for tetrachloropalladate in the presence of a block copolymer surfactant. The copper reductant particles are geometrically self-limiting, so the resulting Pd particles are of similar size. The surfactant induces formation of 10 nm-scale pores within the particles. Some residual copper is alloyed with the Pd, reducing hydrogen storage capacity; use of a more reactive Pd salt can mitigate this. The reaction is conveniently performed in gram-scale batches.

  8. Control of both particle and pore size in nanoporous palladium alloy powders

    DOE PAGESBeta

    Jones, Christopher G.; Cappillino, Patrick J.; Stavila, Vitalie; Robinson, David B.

    2014-07-15

    Energy storage materials often involve chemical reactions with bulk solids. Porosity within the solids can enhance reaction rates. The porosity can be either within or between individual particles of the material. Greater control of the size and uniformity of both types of pore should lead to enhancements of charging and discharging rates in energy storage systems. Furthermore, to control both particle and pore size in nanoporous palladium (Pd)-based hydrogen storage materials, first we created uniformly sized copper particles of about 1 μm diameter by the reduction of copper sulfate with ascorbic acid. In turn, these were used as reducing agentsmore » for tetrachloropalladate in the presence of a block copolymer surfactant. The copper reductant particles are geometrically self-limiting, so the resulting Pd particles are of similar size. The surfactant induces formation of 10 nm-scale pores within the particles. Some residual copper is alloyed with the Pd, reducing hydrogen storage capacity; use of a more reactive Pd salt can mitigate this. The reaction is conveniently performed in gram-scale batches.« less

  9. Scaffolds and cells for tissue regeneration: different scaffold pore sizes-different cell effects.

    PubMed

    Bružauskaitė, Ieva; Bironaitė, Daiva; Bagdonas, Edvardas; Bernotienė, Eiva

    2016-05-01

    During the last decade biomaterial sciences and tissue engineering have become new scientific fields supplying rising demand of regenerative therapy. Tissue engineering requires consolidation of a broad knowledge of cell biology and modern biotechnology investigating biocompatibility of materials and their application for the reconstruction of damaged organs and tissues. Stem cell-based tissue regeneration started from the direct cell transplantation into damaged tissues or blood vessels. However, it is difficult to track transplanted cells and keep them in one particular place of diseased organ. Recently, new technologies such as cultivation of stem cell on the scaffolds and subsequently their implantation into injured tissue have been extensively developed. Successful tissue regeneration requires scaffolds with particular mechanical stability or biodegradability, appropriate size, surface roughness and porosity to provide a suitable microenvironment for the sufficient cell-cell interaction, cell migration, proliferation and differentiation. Further functioning of implanted cells highly depends on the scaffold pore sizes that play an essential role in nutrient and oxygen diffusion and waste removal. In addition, pore sizes strongly influence cell adhesion, cell-cell interaction and cell transmigration across the membrane depending on the various purposes of tissue regeneration. Therefore, this review will highlight contemporary tendencies in application of non-degradable scaffolds and stem cells in regenerative medicine with a particular focus on the pore sizes significantly affecting final recover of diseased organs. PMID:26091616

  10. Pore-size dependent THz absorption of nano-confined water.

    PubMed

    Sun, Chi-Kuang; You, Borwen; Huang, Yu-Ru; Liu, Kao-Hsiang; Sato, Shusaku; Irisawa, Akiyoshi; Imamura, Motoki; Mou, Chung-Yuan

    2015-06-15

    We performed a THz absorption spectroscopy study on liquid water confined in mesoporous silica materials, MCM-41-S-18 and MCM-41-S-21, of two different pore sizes at room temperatures. We found that stronger confinement with a smaller pore size causes reduced THz absorption, indicating reduced water mobility due to confinement. Combined with recent theoretical studies showing that the microscopic structure of water inside the nanopores can be separated into a core water region and an interfacial water region, our spectroscopy analysis further reveals a bulk-water-like THz absorption behavior in the core water region and a solid-like THz absorption behavior in the interfacial water region. PMID:26076248

  11. Porous silicon structures with high surface area/specific pore size

    DOEpatents

    Northrup, M. Allen; Yu, Conrad M.; Raley, Norman F.

    1999-01-01

    Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gasses in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters.

  12. Porous silicon structures with high surface area/specific pore size

    DOEpatents

    Northrup, M.A.; Yu, C.M.; Raley, N.F.

    1999-03-16

    Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gases in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters. 9 figs.

  13. Water Desalination Using Nanoporous Single-Layer Graphene with Tunable Pore Size

    DOE PAGESBeta

    Surwade, Sumedh P.; Smirnov, Sergei N.; Vlassiouk, Ivan V.; Unocic, Raymond R.; Veith, Gabriel M.; Dai, Sheng; Mahurin, Shannon Mark

    2015-03-23

    Graphene has great potential to serve as a separation membrane due to its unique properties such as chemical and mechanical stability, flexibility and most importantly its one-atom thickness. In this study, we demonstrate first experimental evidence of the use of single-layer porous graphene as a desalination membrane. Nanometer-sized pores are introduced into single layer graphene using a convenient oxygen plasma etching process that permits tuning of the pore size. The resulting porous graphene membrane exhibited high rejection of salt ions and rapid water transport, thus functioning as an efficient water desalination membrane. Salt rejection selectivity of nearly 100% and exceptionallymore » high water fluxes exceeding 105 g m-2 s-1 at 40 C were measured using saturated water vapor as a driving force.« less

  14. Improvement of electrospun polymer fiber meshes pore size by femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Rebollar, Esther; Cordero, Diego; Martins, Albino; Chiussi, Stefano; Reis, Rui L.; Neves, Nuno M.; León, Betty

    2011-02-01

    Polymer meshes have recently attracted great attention due to their great variety of applications in fields such as tissue engineering and drug delivery. Poly(ɛ-caprolactone) nanofibers were prepared by electrospinning giving rise to porous meshes. However, for some applications in tissue engineering where, for instance, cell migration into the inner regions of the mesh is aimed, the pore size obtained by conventional techniques is too narrow. To improve the pore size, laser irradiation with femtosecond pulses (i.e., negligible heat diffusion into the polymer material and confined excitation energy) is performed. A detailed study of the influence of the pulse energy, pulse length, and number of pulses on the topography of electrospun fiber meshes has been carried out, and the irradiated areas have been studied by scanning electron microscopy, contact angle measurements and spectroscopic techniques. The results show that using the optimal laser parameters, micropores are formed and the nature of the fibers is preserved.

  15. Water Desalination Using Nanoporous Single-Layer Graphene with Tunable Pore Size

    SciTech Connect

    Surwade, Sumedh P.; Smirnov, Sergei N.; Vlassiouk, Ivan V.; Unocic, Raymond R.; Veith, Gabriel M.; Dai, Sheng; Mahurin, Shannon Mark

    2015-03-23

    Graphene has great potential to serve as a separation membrane due to its unique properties such as chemical and mechanical stability, flexibility and most importantly its one-atom thickness. In this study, we demonstrate first experimental evidence of the use of single-layer porous graphene as a desalination membrane. Nanometer-sized pores are introduced into single layer graphene using a convenient oxygen plasma etching process that permits tuning of the pore size. The resulting porous graphene membrane exhibited high rejection of salt ions and rapid water transport, thus functioning as an efficient water desalination membrane. Salt rejection selectivity of nearly 100% and exceptionally high water fluxes exceeding 105 g m-2 s-1 at 40 C were measured using saturated water vapor as a driving force.

  16. Quantifying fluid distribution and phase connectivity with a simple 3D cubic pore network model constrained by NMR and MICP data

    NASA Astrophysics Data System (ADS)

    Xu, Chicheng; Torres-Verdín, Carlos

    2013-12-01

    A computer algorithm is implemented to construct 3D cubic pore networks that simultaneously honor nuclear magnetic resonance (NMR) and mercury injection capillary pressure (MICP) measurements on core samples. The algorithm uses discretized pore-body size distributions from NMR and pore-throat size versus incremental pore-volume fraction information from MICP as initial inputs. Both pore-throat radius distribution and body-throat correlation are iteratively refined to match percolation-simulated primary drainage capillary pressure with MICP data. It outputs a pore-throat radius distribution which is not directly measurable with either NMR or MICP. In addition, quasi-static fluid distribution and single-phase connectivity are quantified at each capillary pressure stage. NMR measurements on desaturating core samples are simulated from the quantitative fluid distribution in a gas-displacing-water drainage process and are verified with laboratory measurements. We invoke effective medium theory to quantify the single-phase connectivity in two-phase flow by simulating percolation in equivalent sub-pore-networks that consider the remaining fluid phase as solid cementation. Primary drainage relative permeability curves quantified from fluid distribution and phase connectivity show petrophysical consistency after applying a hydrated-water saturation correction. Core measurements of tight-gas sandstone samples from the Cotton Valley formation, East Texas, are used to verify the new algorithm.

  17. Microfluidic Directed Synthesis of Alginate Nanogels with Tunable Pore Size for Efficient Protein Delivery.

    PubMed

    Bazban-Shotorbani, Salime; Dashtimoghadam, Erfan; Karkhaneh, Akbar; Hasani-Sadrabadi, Mohammad Mahdi; Jacob, Karl I

    2016-05-17

    Alginate is a biopolymer with favorable pH-sensitive properties for oral delivery of peptides and proteins. However, conventional alginate nanogels have limitations such as low encapsulation efficiency because of drug leaching during bead preparation and burst release in high pH values. These shortcomings originate from large pore size of the nanogels. In this work, we proposed an on-chip hydrodynamic flow focusing approach for synthesis of alginate nanogels with adjustable pore size to achieve fine-tunable release profile of the encapsulated bioactive agents. It is demonstrated that the microstructure of nanogels can be controlled through adjusting flow ratio and mixing time directed on microfluidic platforms consisting of cross-junction microchannels. In this study, the average pore size of alginate nanogels (i.e., average molecular weight between cross-links, Mc) was related to synthesis parameters. Mc was calculated from equations based on equilibrium swelling theory and proposed methods to modify the theory for pH-sensitive nanogels. In the equations we derived, size and compactness of nanogels are key factors, which can be adjusted by controlling the flow ratio. It was found that increase in flow ratio increases the size of nanogels and decreases their compactness. The size of on-chip generated nanogels for flow ratio of 0.02-0.2 was measured to be in the range of 68-138 nm. Moreover, a method based on the Mie theory was implemented to estimate the aggregation number (Nagg) of polymer chains inside the nanogels as an indicator of compactness. According to the size and compactness results along with equations of modified swelling theory, Mc obtained to be in the range of 0.5-0.8 kDa. The proposed method could be considered as a promising approach for efficient polypeptides encapsulation and their sustained release. PMID:26938744

  18. Controlling drug delivery kinetics from mesoporous titania thin films by pore size and surface energy

    PubMed Central

    Karlsson, Johan; Atefyekta, Saba; Andersson, Martin

    2015-01-01

    The osseointegration capacity of bone-anchoring implants can be improved by the use of drugs that are administrated by an inbuilt drug delivery system. However, to attain superior control of drug delivery and to have the ability to administer drugs of varying size, including proteins, further material development of drug carriers is needed. Mesoporous materials have shown great potential in drug delivery applications to provide and maintain a drug concentration within the therapeutic window for the desired period of time. Moreover, drug delivery from coatings consisting of mesoporous titania has shown to be promising to improve healing of bone-anchoring implants. Here we report on how the delivery of an osteoporosis drug, alendronate, can be controlled by altering pore size and surface energy of mesoporous titania thin films. The pore size was varied from 3.4 nm to 7.2 nm by the use of different structure-directing templates and addition of a swelling agent. The surface energy was also altered by grafting dimethylsilane to the pore walls. The drug uptake and release profiles were monitored in situ using quartz crystal microbalance with dissipation (QCM-D) and it was shown that both pore size and surface energy had a profound effect on both the adsorption and release kinetics of alendronate. The QCM-D data provided evidence that the drug delivery from mesoporous titania films is controlled by a binding–diffusion mechanism. The yielded knowledge of release kinetics is crucial in order to improve the in vivo tissue response associated to therapeutic treatments. PMID:26185444

  19. Fusion Pore Size Limits 5-HT Release From Single Enterochromaffin Cell Vesicles.

    PubMed

    Raghupathi, Ravinarayan; Jessup, Claire F; Lumsden, Amanda L; Keating, Damien J

    2016-07-01

    Enterochromaffin cells are the major site of serotonin (5-HT) synthesis and secretion providing ∼95% of the body's total 5-HT. 5-HT can act as a neurotransmitter or hormone and has several important endocrine and paracrine roles. We have previously demonstrated that EC cells release small amounts of 5-HT per exocytosis event compared to other endocrine cells. We utilized a recently developed method to purify EC cells to demonstrate the mechanisms underlying 5-HT packaging and release. Using the fluorescent probe FFN511, we demonstrate that EC cells express VMAT and that VMAT plays a functional role in 5-HT loading into vesicles. Carbon fiber amperometry studies illustrate that the amount of 5-HT released per exocytosis event from EC cells is dependent on both VMAT and the H(+)-ATPase pump, as demonstrated with reserpine or bafilomycin, respectively. We also demonstrate that increasing the amount of 5-HT loaded into EC cell vesicles does not result in an increase in quantal release. As this indicates that fusion pore size may be a limiting factor involved, we compared pore diameter in EC and chromaffin cells by assessing the vesicle capture of different-sized fluorescent probes to measure the extent of fusion pore dilation. This identified that EC cells have a reduced fusion pore expansion that does not exceed 9 nm in diameter. These results demonstrate that the small amounts of 5-HT released per fusion event in EC cells can be explained by a smaller fusion pore that limits 5-HT release capacity from individual vesicles. PMID:26574734

  20. Numerical simulation of pore size dependent anhydrite precipitation in geothermal reservoirs

    NASA Astrophysics Data System (ADS)

    Mürmann, Mario; Kühn, Michael; Pape, Hansgeorg; Clauser, Christoph

    2013-04-01

    Porosity and permeability of reservoirs are key parameters for an economical use of hot water from geothermal installations and can be significantly reduced by precipitation of minerals, such as anhydrite. The borehole Allermöhe 1 near Hamburg (Germany) represents a failed attempt of geothermal heat mining due to anhydrite precipitation (Baermann et al. 2000). For a risk assessment of future boreholes it is essential to understand how and when anhydrite cementation occurred under reservoir conditions. From core samples of the Allermöhe borehole it was determined that anhydrite precipitation took place in regions of relatively high porosity while regions of low porosity remained uncemented (Wagner et al. 2005). These findings correspond to the fact that e.g. halite precipitation in porous media is found only in relatively large pores (Putnis and Mauthe 2001). This study and others underline that pore size controls crystallization and that it is therefore necessary to establish a relation between pore size and nucleation. The work presented here is based on investigations of Emmanuel and Berkowitz (2007) who present such a relation by applying a thermodynamic approach. However this approach cannot explain the heterogeneous precipitation observed in the Allermöhe core samples. We chose an advanced approach by considering electric system properties resulting in another relation between pore size and crystallization. It is well known that a high fluid supersaturation can be maintained in porous rocks (Putnis and Mauthe 2001). This clearly indicates that a supersaturation threshold exists exceeding thermodynamic equilibrium considerably. In order to quantify spatially heterogeneous anhydrite cementation a theoretical approach was chosen which considered the electric interaction between surface charges of the matrix and calcium and sulphate ions in the fluid. This approach was implemented into the numerical code SHEMAT (Clauser 2003) and used to simulate anhydrite

  1. Control of Porosity and Pore Size of Metal Reinforced Carbon Nanotube Membranes

    PubMed Central

    Dumee, Ludovic; Velleman, Leonora; Sears, Kallista; Hill, Matthew; Schutz, Jurg; Finn, Niall; Duke, Mikel; Gray, Stephen

    2011-01-01

    Membranes are crucial in modern industry and both new technologies and materials need to be designed to achieve higher selectivity and performance. Exotic materials such as nanoparticles offer promising perspectives, and combining both their very high specific surface area and the possibility to incorporate them into macrostructures have already shown to substantially increase the membrane performance. In this paper we report on the fabrication and engineering of metal-reinforced carbon nanotube (CNT) Bucky-Paper (BP) composites with tuneable porosity and surface pore size. A BP is an entangled mesh non-woven like structure of nanotubes. Pure CNT BPs present both very high porosity (>90%) and specific surface area (>400 m2/g). Furthermore, their pore size is generally between 20–50 nm making them promising candidates for various membrane and separation applications. Both electro-plating and electroless plating techniques were used to plate different series of BPs and offered various degrees of success. Here we will report mainly on electroless plated gold/CNT composites. The benefit of this method resides in the versatility of the plating and the opportunity to tune both average pore size and porosity of the structure with a high degree of reproducibility. The CNT BPs were first oxidized by short UV/O3 treatment, followed by successive immersion in different plating solutions. The morphology and properties of these samples has been investigated and their performance in air permeation and gas adsorption will be reported. PMID:24957493

  2. Impact of pore size on the sorption of uranyl under seawater conditions

    DOE PAGESBeta

    Mayes, Richard T.; Gorka, Joanna; Dai, Sheng

    2016-04-05

    The extraction of uranium from seawater has received significant interest recently, because of the possibility of a near-limitless supply of uranium to fuel the nuclear power industry. While sorbent development has focused primarily on polymeric sorbents, nanomaterials represent a new area that has the potential to surpass the current polymeric sorbents, because of the high surface areas that are possible. Mesoporous carbon materials are a stable, high-surface-area material capable of extracting various chemical species from a variety of environments. Herein, we report the use of a dual templating process to understand the effect of pore size on the adsorption ofmore » uranyl ions from a uranyl brine consisting of seawater-relevant sodium, chloride, and bicarbonate ions. It was found that pore size played a more significant role in the effective use of the grafted polymer, leading to higher uranium capacities than the surface area. Furthermore, the pore size must be tailored to meet the demands of the extraction medium and analyte metal to achieve efficacy as an adsorbent.« less

  3. On dependence of mechanical properties of brittle material on partial concentrations of different sized pores in its structure in a wide range of porosity

    NASA Astrophysics Data System (ADS)

    Konovalenko, Igor S.; Smolin, Alexey Yu.; Psakhie, Sergey G.

    2015-10-01

    2D and 3D models of mechanical behavior of brittle porous material under uniaxial compression loading were developed in the framework of the movable cellular automaton method. The considered material was characterized by pore size distribution function having two maxima. On the basis of simulation results the dependence of the strength properties of brittle porous material on its total porosity and partial porosities corresponding to pores with different size was revealed. The change in internal structure of material in a wide range of mentioned parameters was analyzed. The main structural factors influencing compression strength of the material at various combinations of values of porosity parameters were identified.

  4. Microtomography and pore-scale modeling of two-phase Fluid Distribution

    SciTech Connect

    Silin, D.; Tomutsa, L.; Benson, S.; Patzek, T.

    2010-10-19

    Synchrotron-based X-ray microtomography (micro CT) at the Advanced Light Source (ALS) line 8.3.2 at the Lawrence Berkeley National Laboratory produces three-dimensional micron-scale-resolution digital images of the pore space of the reservoir rock along with the spacial distribution of the fluids. Pore-scale visualization of carbon dioxide flooding experiments performed at a reservoir pressure demonstrates that the injected gas fills some pores and pore clusters, and entirely bypasses the others. Using 3D digital images of the pore space as input data, the method of maximal inscribed spheres (MIS) predicts two-phase fluid distribution in capillary equilibrium. Verification against the tomography images shows a good agreement between the computed fluid distribution in the pores and the experimental data. The model-predicted capillary pressure curves and tomography-based porosimetry distributions compared favorably with the mercury injection data. Thus, micro CT in combination with modeling based on the MIS is a viable approach to study the pore-scale mechanisms of CO{sub 2} injection into an aquifer, as well as more general multi-phase flows.

  5. Systematic Design of Pore Size and Functionality in Isoreticular MOFs and Their Application in Methane Storage

    NASA Astrophysics Data System (ADS)

    Eddaoudi, Mohamed; Kim, Jaheon; Rosi, Nathaniel; Vodak, David; Wachter, Joseph; O'Keeffe, Michael; Yaghi, Omar M.

    2002-01-01

    A strategy based on reticulating metal ions and organic carboxylate links into extended networks has been advanced to a point that allowed the design of porous structures in which pore size and functionality could be varied systematically. Metal-organic framework (MOF-5), a prototype of a new class of porous materials and one that is constructed from octahedral Zn-O-C clusters and benzene links, was used to demonstrate that its three-dimensional porous system can be functionalized with the organic groups -Br, -NH2, -OC3H7, -OC5H11, -C2H4, and -C4H4 and that its pore size can be expanded with the long molecular struts biphenyl, tetrahydropyrene, pyrene, and terphenyl. We synthesized an isoreticular series (one that has the same framework topology) of 16 highly crystalline materials whose open space represented up to 91.1% of the crystal volume, as well as homogeneous periodic pores that can be incrementally varied from 3.8 to 28.8 angstroms. One member of this series exhibited a high capacity for methane storage (240 cubic centimeters at standard temperature and pressure per gram at 36 atmospheres and ambient temperature), and others the lowest densities (0.41 to 0.21 gram per cubic centimeter) for a crystalline material at room temperature.

  6. Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage.

    PubMed

    Eddaoudi, Mohamed; Kim, Jaheon; Rosi, Nathaniel; Vodak, David; Wachter, Joseph; O'Keeffe, Michael; Yaghi, Omar M

    2002-01-18

    A strategy based on reticulating metal ions and organic carboxylate links into extended networks has been advanced to a point that allowed the design of porous structures in which pore size and functionality could be varied systematically. Metal-organic framework (MOF-5), a prototype of a new class of porous materials and one that is constructed from octahedral Zn-O-C clusters and benzene links, was used to demonstrate that its three-dimensional porous system can be functionalized with the organic groups -Br, -NH2, -OC3H7, -OC5H11, -C2H4, and -C4H4 and that its pore size can be expanded with the long molecular struts biphenyl, tetrahydropyrene, pyrene, and terphenyl. We synthesized an isoreticular series (one that has the same framework topology) of 16 highly crystalline materials whose open space represented up to 91.1% of the crystal volume, as well as homogeneous periodic pores that can be incrementally varied from 3.8 to 28.8 angstroms. One member of this series exhibited a high capacity for methane storage (240 cubic centimeters at standard temperature and pressure per gram at 36 atmospheres and ambient temperature), and others the lowest densities (0.41 to 0.21 gram per cubic centimeter) for a crystalline material at room temperature. PMID:11799235

  7. Size-dependent leak of soluble and membrane proteins through the yeast nuclear pore complex

    PubMed Central

    Popken, Petra; Ghavami, Ali; Onck, Patrick R.; Poolman, Bert; Veenhoff, Liesbeth M.

    2015-01-01

    Nuclear pore complexes (NPCs) allow selective import and export while forming a barrier for untargeted proteins. Using fluorescence microscopy, we measured in vivo the permeability of the Saccharomyces cerevisiae NPC for multidomain proteins of different sizes and found that soluble proteins of 150 kDa and membrane proteins with an extralumenal domain of 90 kDa were still partly localized in the nucleus on a time scale of hours. The NPCs thus form only a weak barrier for the majority of yeast proteins, given their monomeric size. Using FGΔ-mutant strains, we showed that specific combinations of Nups, especially with Nup100, but not the total mass of FG-nups per pore, were important for forming the barrier. Models of the disordered phase of wild-type and mutant NPCs were generated using a one bead per amino acid molecular dynamics model. The permeability measurements correlated with the density predictions from coarse-grained molecular dynamics simulations in the center of the NPC. The combined in vivo and computational approach provides a framework for elucidating the structural and functional properties of the permeability barrier of nuclear pore complexes. PMID:25631821

  8. Influence of the pore size in multi-walled carbon nanotubes on the hydrogen storage behaviors

    SciTech Connect

    Lee, Seul-Yi; Park, Soo-Jin

    2012-10-15

    Activated multi-walled carbon nanotubes (A-MWCNTs) were prepared using a chemical activation method to obtain well-developed pore structures for use as hydrogen storage materials. The microstructure and crystallinity of the A-MWCNTs were evaluated by X-ray diffraction and Fourier transform Raman spectroscopy. The textural properties of the A-MWCNTs were investigated by nitrogen gas sorption analysis at 77 K. The hydrogen storage capacity of the A-MWCNTs was evaluated at 77 K and 1 bar. The results showed that the specific surface area of the MWCNTs increased from 327 to 495 m{sup 2}/g as the activation temperature was increased. The highest hydrogen storage capacity was observed in the A-MWCNTs sample activated at 900 Degree-Sign C (0.54 wt%). This was attributed to it having the narrowest microporosity, which is a factor closely related to the hydrogen storage capacity. This shows that the hydrogen storage behaviors depend on the pore volume. Although a high pore volume is desirable for hydrogen storage, it is also severely affected if the pore size in the A-MWCNTs for the hydrogen molecules is suitable for creating the activation process. Highlights: Black-Right-Pointing-Pointer The AT-800 and AT-900 samples were prepared by a chemical activation method at activation temperature of 800 and 900 Degree-Sign C, respectively. Black-Right-Pointing-Pointer The AT-900 sample has the narrowest peak in comparison with the AT-800 sample, resulting from the overlap of the two peaks (Peak I and Peak II). Black-Right-Pointing-Pointer This overlapping effect is due to the newly created micropores or shrinkages of pores in Peak II. So, these determining characteristics are essential for designing materials that are suitable for molecular hydrogen storage.

  9. Porosity, Pore Size, and Permeability of Sediments from Site C0002, IODP Expedition 338

    NASA Astrophysics Data System (ADS)

    Dugan, B.; Huepers, A.; Song, I.; Kitajima, H.; Esteban, L.

    2013-12-01

    Mercury injection capillary pressure (MICP) measurements were made on cuttings and core samples from Integrated Ocean Drilling Program (IODP) Site C0002 to evaluate porosity, pore throat size, and permeability of mud(stone) at the centerpiece drill site of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). Core samples from 221-464 meters below sea floor (mbsf) in the Kumano forearc basin have MICP-determined porosities from 40-56%, median pore radii from 0.077-0.205 microns, and permeability from 3.3x10-10 - 2.0x10-9 m2. The porosity of these core samples is similar to shipboard porosity determined from moisture and density (MAD) analyses. During IODP Expedition 338 cuttings samples were recovered from ~865-2005 mbsf during riser drilling at Site C0002F. MICP analyses of cuttings samples, greater than 4 mm size fraction, from 928-1980 mbsf in the inner wedge of the accretionary prism constrain porosities from 21-44%, median pore radii from 0.021-0.032 microns, and permeability from 1.2x10-11 - 1.6x10-10 m2. The porosity of these cuttings samples is consistently lower than the MAD-determined porosity on cuttings from the >4mm size fraction, however the values are consistent with core-based, MAD-derived porosity from Hole C0002B above 1057 mbsf and with cuttings-based, MAD-derived porosity on select samples from 1700-2000 mbsf that were determined to be intact formation and not influenced by drilling disturbance. These results suggest that select formation cuttings or MICP-analyses can help define in situ porosity. Additional post-expedition research will be used to better understand the ability of MICP data to define mudstone permeability and to constrain permeability-porosity and permeability-grain size-pore throat relations for sediments at Site C0002. A detailed model of permeability and porosity behavior will inform modeling studies of pore pressure generation and fluid and heat transport.

  10. Evaluation of immunoglobulin adsorption on the hydrophobic charge-induction resins with different ligand densities and pore sizes.

    PubMed

    Lu, Hui-Li; Lin, Dong-Qiang; Gao, Dong; Yao, Shan-Jing

    2013-02-22

    Hydrophobic charge-induction chromatography (HCIC) is a novel technology for antibody purification. The ligand densities and pore properties of HCIC resins have significant effects on the separation behavior of protein, however, the understandings are quite limited. In the present work, new HCIC ligand, 2-mercapto-1-methylimidazole (MMI) was coupled to three agarose matrices with different pore sizes. A series of MMI resins with different ligand density and pore size was prepared by the control of ligand coupling. The adsorption isotherms and kinetics on the series of MMI resins were investigated with bovine serum immunoglobulin as the model IgG, and the effects of salt addition were studied. The Langmuir equation and pore diffusion model were used to fit the experimental data, and the influences of ligand density, pore size and salt addition on the saturated adsorption capacity, the dissociation constant and the effective diffusivity were discussed. It was found that the adsorption capacities and the effective pore diffusion coefficient increased with the increase of ligand density and pore size. The effects of salt addition on the adsorption behaviors were dependent on the ligand density. For low ligand density the IgG adsorption was salt-promoted, while the resins with high ligand density showed a salt-independent property. The results indicated that for a given protein the ligand density and pore size of HCIC resins should be optimized for improving the protein adsorption. PMID:23336945

  11. Reversible control of pore size and surface chemistry of mesoporous silica through dynamic covalent chemistry: philicity mediated catalysis

    NASA Astrophysics Data System (ADS)

    Singh, Dheeraj Kumar; Pavan Kumar, B. V. V. S.; Eswaramoorthy, M.

    2015-08-01

    Here, we report the synthesis of adaptive hybrid mesoporous silica having the ability to reconfigure its pore properties such as pore size and philicity in response to the external environment. Decyl chains were reversibly appended to the pore walls of silica through imine motifs as dynamic covalent modules to switch the pore size and philicity in response to pH. This switching of pore properties was used to gate the access of reactants to the gold nanoparticles immobilized inside the nanopores, thus enabling us to turn-on/turn-off the catalytic reaction. The use of such dynamic covalent modules to govern pore properties would enable the realization of intelligent hybrids capable of controlling many such chemical processes in response to stimuli.Here, we report the synthesis of adaptive hybrid mesoporous silica having the ability to reconfigure its pore properties such as pore size and philicity in response to the external environment. Decyl chains were reversibly appended to the pore walls of silica through imine motifs as dynamic covalent modules to switch the pore size and philicity in response to pH. This switching of pore properties was used to gate the access of reactants to the gold nanoparticles immobilized inside the nanopores, thus enabling us to turn-on/turn-off the catalytic reaction. The use of such dynamic covalent modules to govern pore properties would enable the realization of intelligent hybrids capable of controlling many such chemical processes in response to stimuli. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02959g

  12. Pore Scale Heterogeneity in the Mineral Distribution, Surface Area and Adsorption in Porous Rocks

    NASA Astrophysics Data System (ADS)

    Lai, P. E. P.; Krevor, S. C.

    2014-12-01

    The impact of heterogeneity in chemical transport and reaction is not understood in continuum (Darcy/Fickian) models of reactive transport. This is manifested in well-known problems such as scale dependent dispersion and discrepancies in reaction rate observations made at laboratory and field scales [1]. Additionally, this is a source of uncertainty for carbon dioxide injection, which produces a reactive fluid-rock system particularly in carbonate rock reservoirs. A potential cause is the inability of the continuum approach to incorporate the impact of heterogeneity in pore-scale reaction rates. This results in part from pore-scale heterogeneities in surface area of reactive minerals [2, 3]. We use x-ray micro tomography to describe the non-normal 3-dimensional distribution of reactive surface area within a porous medium according to distinct mineral groups. Using in-house image processing techniques, thin sections, nitrogen BET surface area, backscattered electron imaging and energy dispersive spectroscopy, we compare the surface area of each mineral phase to those obtained from x-ray CT imagery. In all samples, there is little correlation between the reactive surface area fraction and the volumetric fraction of a mineral in a bulk rock. Berea sandstone was far less heterogeneous and has a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. In carbonates, heterogeneity is more complex and surface area must be characterized at multiple length scales for an accurate description of reactive transport. We combine the mineral specific surface area characterisation to dynamic tomography, imaging the flow of water and solutes, to observe flow dependent and mineral specific adsorption. The observations may contribute to the incorporation of experimentally based statistical descriptions of pore scale heterogeneity in reactive transport into upscaled models, moving it closer to predictive capabilities for field scale

  13. Scaling in animal group-size distributions

    PubMed Central

    Bonabeau, Eric; Dagorn, Laurent; Fréon, Pierre

    1999-01-01

    An elementary model of animal aggregation is presented. The group-size distributions resulting from this model are truncated power laws. The predictions of the model are found to be consistent with data that describe the group-size distributions of tuna fish, sardinellas, and African buffaloes. PMID:10200286

  14. Body Size Distribution of the Dinosaurs

    PubMed Central

    O’Gorman, Eoin J.; Hone, David W. E.

    2012-01-01

    The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size. PMID:23284818

  15. An integrated approach for determination of pore-type distribution in carbonate-siliciclastic Asmari Reservoir, Cheshmeh-Khosh Oilfield, SW Iran

    NASA Astrophysics Data System (ADS)

    Gharechelou, Sajjad; Amini, Abdolhossein; Kadkhodaie-Ilkhchi, Ali; Moradi, Babak

    2015-10-01

    This paper presents an integrated pore type study at microscopic (core data), mesoscopic (well logs) and megascopic scales (3D seismic data) in the mixed carbonate-siliciclastic Asmari Reservoir of the Cheshmeh-Khosh Oilfield, SW Iran. Firstly, pore types are determined in a microscopic scale based on petrographic studies of thin sections. Well logs and nuclear magnetic resonance (NMR) log data are employed for pore type determination based on a velocity deviation log (mesoscopic scale). For each pore type subclass, a suite of physical rock properties including average poroperm values, T2 distribution, capillary pressure, pore size distribution and depositional texture are calculated. For this purpose, the NMR log, mercury injection capillary pressure data and core descriptions are interpreted in an integrated approach. Capillary pressure and pore size distribution in each pore type class are determined by mercury injection capillary pressure tests and synthesis of a continuous capillary pressure log from the NMR log (pseudo Pc curves). For dynamic behavior examination of the reservoir, the pore types are analysed in the framework of hydraulic flow units. Finally, 3D post-stacked seismic data are converted to a cube of pore types based on acoustic impedance inversion and seismic attributes. The methodology of this study is accomplished by using core and log data from three key wells and a 3D post-stack seismic data from the studied field. Lastly, a map of pore type distribution is established to provide a clue on the high and low permeable zones of the field. The presented methodology signifies reservoir anatomy on micro to mega scales.

  16. Optimization of protein fractionation by skim milk microfiltration: Choice of ceramic membrane pore size and filtration temperature.

    PubMed

    Jørgensen, Camilla Elise; Abrahamsen, Roger K; Rukke, Elling-Olav; Johansen, Anne-Grethe; Schüller, Reidar B; Skeie, Siv B

    2016-08-01

    The objective of this study was to investigate how ceramic membrane pore size and filtration temperature influence the protein fractionation of skim milk by cross flow microfiltration (MF). Microfiltration was performed at a uniform transmembrane pressure with constant permeate flux to a volume concentration factor of 2.5. Three different membrane pore sizes, 0.05, 0.10, and 0.20µm, were used at a filtration temperature of 50°C. Furthermore, at pore size 0.10µm, 2 different filtration temperatures were investigated: 50 and 60°C. The transmission of proteins increased with increasing pore size, giving the permeate from MF with the 0.20-µm membrane a significantly higher concentration of native whey proteins compared with the permeates from the 0.05- and 0.10-µm membranes (0.50, 0.24, and 0.39%, respectively). Significant amounts of caseins permeated the 0.20-µm membrane (1.4%), giving a permeate with a whitish appearance and a casein distribution (αS2-CN: αS1-CN: κ-CN: β-CN) similar to that of skim milk. The 0.05- and 0.10-µm membranes were able to retain all caseins (only negligible amounts were detected). A permeate free from casein is beneficial in the production of native whey protein concentrates and in applications where transparency is an important functional characteristic. Microfiltration of skim milk at 50°C with the 0.10-µm membrane resulted in a permeate containing significantly more native whey proteins than the permeate from MF at 60°C. The more rapid increase in transmembrane pressure and the significantly lower concentration of caseins in the retentate at 60°C indicated that a higher concentration of caseins deposited on the membrane, and consequently reduced the native whey protein transmission. Optimal protein fractionation of skim milk into a casein-rich retentate and a permeate with native whey proteins were obtained by 0.10-µm MF at 50°C. PMID:27265169

  17. Choice of pore size can introduce artefacts when filtering picoeukaryotes for molecular biodiversity studies.

    PubMed

    Sørensen, Nikolaj; Daugbjerg, Niels; Richardson, Katherine

    2013-05-01

    Published results of studies based on samples size fractionated by sequential filtration (e.g. 0.2-3 μm) indicate that many ciliate, dinoflagellate and rhizarian phylotypes are found among marine picoeukaryotes. This is somewhat surprising as these protists are typically known as being large organisms (often >10 μm) and no picoplanktonic species have so far been identified. Here, the abundances of ciliate and dinoflagellate phylotypes in published molecular studies of picoeukaryotes are shown to correlate negatively with the pore size chosen for the end filter in the sequential filtrations (i.e. the filter used to collect the microbial biomass). This suggests that extracellular DNA adhering to small particles may be the source of ciliate and dinoflagellate phylotypes in picoplanktonic size fractions. This hypothesis was confirmed using real-time qPCR, which revealed significantly less dinoflagellate 18S rDNA in a 0.8-3-μm size fraction compared to 0.2-3 μm. On average, the abundance of putative extracellular phylotypes decreased by 84-89 % when a 0.8- μm end filter was used rather than a 0.2-μm end filter. A 0.8-μm filter is, however, not sufficient to retain all picoeukaryotic cells. Thus, selection of filter pore size involves a trade-off between avoiding artefacts generated by extracellular DNA and sampling the entire picoeukaryotic community. In contrast to ciliate and dinoflagellate phylotypes, rhizarian phylotypes in the picoplankton size range do not display a pattern consistent with an extracellular origin. This is likely due to the documented existence of picoplanktonic swarmer cells within this group. PMID:23325466

  18. Experimental determination of size distributions: analyzing proper sample sizes

    NASA Astrophysics Data System (ADS)

    Buffo, A.; Alopaeus, V.

    2016-04-01

    The measurement of various particle size distributions is a crucial aspect for many applications in the process industry. Size distribution is often related to the final product quality, as in crystallization or polymerization. In other cases it is related to the correct evaluation of heat and mass transfer, as well as reaction rates, depending on the interfacial area between the different phases or to the assessment of yield stresses of polycrystalline metals/alloys samples. The experimental determination of such distributions often involves laborious sampling procedures and the statistical significance of the outcome is rarely investigated. In this work, we propose a novel rigorous tool, based on inferential statistics, to determine the number of samples needed to obtain reliable measurements of size distribution, according to specific requirements defined a priori. Such methodology can be adopted regardless of the measurement technique used.

  19. Effect of collagen-glycosaminoglycan scaffold pore size on matrix mineralization and cellular behavior in different cell types.

    PubMed

    Murphy, Ciara M; Duffy, Garry P; Schindeler, Aaron; O'brien, Fergal J

    2016-01-01

    We have previously examined osteoblast behavior on porous collagen-glycosaminoglycan (CG) scaffolds with a range of mean pore sizes demonstrating superior cell attachment and migration in scaffolds with the largest pores (325 μm). Scaffolds provide a framework for construct development; therefore, it is crucial to identify the optimal pore size for augmented tissue formation. Utilizing the same range of scaffolds (85 μm - 325 μm), this study aimed to examine the effects of mean pore size on subsequent osteoblast differentiation and matrix mineralization, and to understand the mechanism by which pore size influences behavior of different cell types. Consequently, primary mesenchymal stem cells (MSCs) were assessed and their behavior compared to osteoblasts. Results demonstrated that scaffolds with the largest pore size (325 μm) facilitated improved osteoblast infiltration, earlier expression of mature bone markers osteopontin (OPN) and osteocalcin (OCN), and increased mineralization. MSCs responded similarly to osteoblasts whereby cell attachment and scaffold infiltration improved with increasing pore size. However, MSCs showed reduced cell motility, proliferation, and scaffold infiltration compared to osteoblasts. This was associated with differences in the profile of integrin subunits (α2) and collagen receptors (CD44), indicating that osteoblasts have a stronger affinity for CG scaffolds compared to MSCs. In summary, these results reveal how larger pores promote improved cell infiltration, essential for construct development, however the optimal scaffold pore size can be cell type specific. As such, this study highlights a necessity to tailor both scaffold micro-architecture and cell-type when designing constructs for successful bone tissue engineering applications. PMID:26386362

  20. Micro and nano-size pores of clay minerals in shale reservoirs: Implication for the accumulation of shale gas

    NASA Astrophysics Data System (ADS)

    Chen, Shangbin; Han, Yufu; Fu, Changqin; Zhang, han; Zhu, Yanming; Zuo, Zhaoxi

    2016-08-01

    A pore is an essential component of shale gas reservoirs. Clay minerals are the adsorption carrier second only to organic matter. This paper uses the organic maturity test, Field-Emission Scanning Electron Microscopy (FE-SEM), and X-ray Diffraction (XRD) to study the structure and effect of clay minerals on storing gas in shales. Results show the depositional environment and organic maturity influence the content and types of clay minerals as well as their structure in the three types of sedimentary facies in China. Clay minerals develop multi-size pores which shrink to micro- and nano-size by close compaction during diagenesis. Micro- and nano-pores can be divided into six types: 1) interlayer, 2) intergranular, 3) pore and fracture in contact with organic matter, 4) pore and fracture in contact with other types of minerals, 5) dissolved and, 6) micro-cracks. The contribution of clay minerals to the presence of pores in shale is evident and the clay plane porosity can even reach 16%, close to the contribution of organic matter. The amount of clay minerals and pores displays a positive correlation. Clay minerals possess a strong adsorption which is affected by moisture and reservoir maturity. Different pore levels of clay minerals are mutually arranged, thus essentially producing distinct reservoir adsorption effects. Understanding the structural characteristics of micro- and nano-pores in clay minerals can provide a tool for the exploration and development of shale gas reservoirs.

  1. Effective pore size and radius of capture for K(+) ions in K-channels.

    PubMed

    Moldenhauer, Hans; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

    2016-01-01

    Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (r(E)) in several K-channel crystal structures. r(E) was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent r(E) estimates for MthK and Kv1.2/2.1 structures, with r(E) = 5.3-5.9 Å and r(E) = 4.5-5.2 Å, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (r(C)) for two electrophysiological counterparts, the large conductance calcium activated K-channel (r(C) = 2.2 Å) and the Shaker Kv-channel (r(C) = 0.8 Å), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between r(E) and r(C), produced consistent size radii of 3.1-3.7 Å and 3.6-4.4 Å for hydrated K(+) ions. These hydrated K(+) estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively. PMID:26831782

  2. Effective pore size and radius of capture for K+ ions in K-channels

    PubMed Central

    Moldenhauer, Hans; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

    2016-01-01

    Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (rE) in several K-channel crystal structures. rE was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent rE estimates for MthK and Kv1.2/2.1 structures, with rE = 5.3–5.9 Å and rE = 4.5–5.2 Å, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (rC) for two electrophysiological counterparts, the large conductance calcium activated K-channel (rC = 2.2 Å) and the Shaker Kv-channel (rC = 0.8 Å), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between rE and rC, produced consistent size radii of 3.1–3.7 Å and 3.6–4.4 Å for hydrated K+ ions. These hydrated K+ estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively. PMID:26831782

  3. INITIAL SIZE AND DYNAMICS OF VIRAL FUSION PORES ARE A FUNCTION OF THE FUSION PROTEIN MEDIATING MEMBRANE FUSION

    PubMed Central

    Plonsky, I.; Kingsley, D. H.; Rashtian, A.; Blank, P.S.; Zimmerberg, J.

    2013-01-01

    To investigate the role of the fusogenic protein in the initial size and dynamics of the pore that widens to finalize membrane fusion, two different fusion proteins expressed in the same cell line were investigated: the major glycoprotein of baculovirus Autographa californica (GP64) and the hemaggluttinin of influenza X31 (HA). The host Sf9 cells expressing these viral proteins, irrespective of protein species, fused to human red blood cells (RBC) upon acidification of the medium. High time resolution electrophysiological study of fusion pore conductance revealed fundamental differences in a) the initial pore conductance (pores created by HA were smaller than those created by GP64), b) the ability of pores to flicker (only HA-mediated pores flickered), and c) the time required for pore formation (HA-mediated pores took much longer to form following acidification). Thus 1) HA and GP64 have divergent electrophysiological phenotypes even when they fuse identical membranes, and 2) fusion proteins play a crucial role in determining initial fusion pore characteristics. The structure of the initial fusion pore detected by electrical conductance measurements is sensitive to the nature of the fusion protein. PMID:18208404

  4. Asteroid Size-Frequency Distribution

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    2001-01-01

    A total of six deep exposures (using AOT CAM01 with a 6 inch PFOV) through the ISOCAM LW10 filter (IRAS Band 1, i.e. 12 micron) were obtained on an approximately 15 arcminute square field centered on the ecliptic plane. Point sources were extracted using the technique described. Two known asteroids appear in these frames and 20 sources moving with velocities appropriate for main belt asteroids are present. Most of the asteroids detected have flux densities less than 1 mJy, i,e., between 150 and 350 times fainter than any of the asteroids observed by IRAS. These data provide the first direct measurement of the 12 pm sky-plane density for asteroids on the ecliptic equator. The median zodiacal foreground, as measured by ISOCAM during this survey, is found to be 22.1 +/- 1.5 mJy per pixel, i.e., 26.2 +/- 1.7 MJy/sr. The results presented here imply that the actual number of kilometer-sized asteroids is significantly greater than previously believed and in reasonable agreement with the Statistical Asteroid Model.

  5. Size distributions of solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Cliver, E.; Reames, D.; Kahler, S.; Cane, H.

    1991-01-01

    NASA particle detectors on the IMP-8 are employed to determine the size distributions of the peak fluxes of events related to solar-energetic particles including protons and electrons. The energetic proton events show a flatter size distribution which suggests that not all flares are proton flares. Both the electron and proton events are classified as either 'impulsive' or 'gradual', and the impulsive events tend to have a steeper power-law distribution.

  6. Characterization and structural investigation of fractal porous-silica over an extremely wide scale range of pore size.

    PubMed

    Ono, Yusuke; Mayama, Hiroyuki; Furó, István; Sagidullin, Alexander I; Matsushima, Keiichiro; Ura, Haruo; Uchiyama, Tomoyuki; Tsujii, Kaoru

    2009-08-01

    We have succeeded in creating Menger sponge-like fractal body, i.e., porous-silica samples with Menger sponge-like fractal geometries, by a novel template method utilizing template particles of alkylketene dimer (AKD) and a sol-gel synthesis of tetramethyl orthosilicate (TMOS). We report here the first experimental results on characterization and structural investigations of the fractal porous-silica samples prepared with various conditions such as calcination temperature and packing condition of the template particles. In order to characterize the fractal porous-silica samples, pore volume distribution, porosity and specific surface area were measured over an extremely wide scale from 1 nm to 100 microm by means of mercury porosimetry, (1)H NMR cryoporometry, nitrogen gas adsorption experiments together with direct evaluations of cross-sectional fractal dimension D(cs), and size limits of D(cs). We have found that the pore volume distribution and specific surface area of the fractal porous-silica samples can be discussed in terms of different fractal porous structures at different scale regions. PMID:19406424

  7. Anodic aluminum oxide with fine pore size control for selective and effective particulate matter filtering

    NASA Astrophysics Data System (ADS)

    Zhang, Su; Wang, Yang; Tan, Yingling; Zhu, Jianfeng; Liu, Kai; Zhu, Jia

    2016-07-01

    Air pollution is widely considered as one of the most pressing environmental health issues. Particularly, atmospheric particulate matters (PM), a complex mixture of solid or liquid matter suspended in the atmosphere, are a harmful form of air pollution due to its ability to penetrate deep into the lungs and blood streams, causing permanent damages such as DNA mutations and premature death. Therefore, porous materials which can effectively filter out particulate matters are highly desirable. Here, for the first time, we demonstrate that anodic aluminum oxide with fine pore size control fabricated through a scalable process can serve as effective and selective filtering materials for different types of particulate matters (such as PM2.5, PM10). Combining selective and dramatic filtering effect, fine pore size control and a scalable process, this type of anodic aluminum oxide templates can potentially serve as a novel selective filter for different kinds of particulate matters, and a promising and complementary solution to tackle this serious environmental issue.

  8. Particle size distribution instrument. Topical report 13

    SciTech Connect

    Okhuysen, W.; Gassaway, J.D.

    1995-04-01

    The development of an instrument to measure the concentration of particles in gas is described in this report. An in situ instrument was designed and constructed which sizes individual particles and counts the number of occurrences for several size classes. Although this instrument was designed to detect the size distribution of slag and seed particles generated at an experimental coal-fired magnetohydrodynamic power facility, it can be used as a nonintrusive diagnostic tool for other hostile industrial processes involving the formation and growth of particulates. Two of the techniques developed are extensions of the widely used crossed beam velocimeter, providing simultaneous measurement of the size distribution and velocity of articles.

  9. Pore size controls on the base of the methane hydrate stability zone in the Kumano Basin, offshore Japan

    NASA Astrophysics Data System (ADS)

    Daigle, Hugh; Dugan, Brandon

    2014-11-01

    The base of the methane hydrate stability zone (MHSZ) in the Kumano Basin, offshore Japan, is marked by a bottom-simulating reflection (BSR) on seismic data. At Integrated Ocean Drilling Program Site C0002, which penetrates this BSR, the in situ temperature profile combined with bulk seawater methane equilibrium conditions suggest that the base of the MHSZ is 428 m below seafloor (bsf), which is 28 m deeper than the observed BSR (400 m bsf). We found that submicron pore sizes determined by mercury injection capillary pressure are sufficiently small to cause 64% of the observed uplift of the base of the MHSZ by the Gibbs-Thomson effect. This is the most thorough characterization of pore sizes within the MHSZ performed to date and illustrates the extent to which pore size can influence MHSZ thickness. Our results demonstrate the importance of considering lithology and pore structure when assessing methane hydrate stability conditions in marine sediments.

  10. Domain Size Distribution in Segregating Binary Superfluids

    NASA Astrophysics Data System (ADS)

    Takeuchi, Hiromitsu

    2016-05-01

    Domain size distribution in phase separating binary Bose-Einstein condensates is studied theoretically by numerically solving the Gross-Pitaevskii equations at zero temperature. We show that the size distribution in the domain patterns arising from the dynamic instability obeys a power law in a scaling regime according to the dynamic scaling analysis based on the percolation theory. The scaling behavior is kept during the relaxation dynamics until the characteristic domain size becomes comparable to the linear size of the system, consistent with the dynamic scaling hypothesis of the phase-ordering kinetics. Our numerical experiments indicate the existence of a different scaling regime in the size distribution function, which can be caused by the so-called coreless vortices.

  11. Analytic modeling of aerosol size distributions

    NASA Technical Reports Server (NTRS)

    Deepack, A.; Box, G. P.

    1979-01-01

    Mathematical functions commonly used for representing aerosol size distributions are studied parametrically. Methods for obtaining best fit estimates of the parameters are described. A catalog of graphical plots depicting the parametric behavior of the functions is presented along with procedures for obtaining analytical representations of size distribution data by visual matching of the data with one of the plots. Examples of fitting the same data with equal accuracy by more than one analytic model are also given.

  12. Micron-pore-sized metallic filter tube membranes for filtration of particulates and water purification

    SciTech Connect

    Phelps, Tommy Joe; Palumbo, Anthony Vito; Fagan, Lisa Anne; Bischoff, Brian L; Miller, Curtis Jack; Drake, Meghan M; Judkins, Roddie Reagan

    2008-01-01

    Robust filtering techniques capable of efficiently removing particulates and biological agents from water or air suffer from plugging, poor rejuvenation, low permeance, and high backpressure. Operational characteristics of pressure-driven separations are in part controlled by the membrane pore size, charge of particulates, transmembrane pressure and the requirement for sufficient water flux to overcome fouling. With long term use filters decline in permeance due to filter-cake plugging of pores, fouling, or filter deterioration. Though metallic filter tube development at ORNL has focused almost exclusively on gas separations, a small study examined the applicability of these membranes for tangential filtering of aqueous suspensions of bacterial-sized particles. A mixture of fluorescent polystyrene microspheres ranging in size from 0.5 to 6 {micro}m in diameter simulated microorganisms in filtration studies. Compared to a commercial filter, the ORNL 0.6 {micro}m filter averaged approximately 10-fold greater filtration efficiency of the small particles, several-fold greater permeance after considerable use and it returned to approximately 85% of the initial flow upon backflushing versus 30% for the commercial filter. After filtering several liters of the particle-containing suspension, the ORNL composite filter still exhibited greater than 50% of its initial permeance while the commercial filter had decreased to less than 20%. When considering a greater filtration efficiency, greater permeance per unit mass, greater percentage of rejuvenation upon backflushing (up to 3-fold), and likely greater performance with extended use, the ORNL 0.6 {micro}m filters can potentially outperform the commercial filter by factors of 100-1000 fold.

  13. Soil signature simulation of complex mixtures and particle size distributions

    NASA Astrophysics Data System (ADS)

    Carson, Tyler; Bachmann, Charles M.; Salvaggio, Carl

    2015-09-01

    Soil reflectance signatures were modeled using the digital imaging and remote sensing image generation model and Blender three-dimensional (3-D) graphic design software. Using these tools, the geometry, radiometry, and chemistry of quartz and magnetite were exploited to model the presence of particle size and porosity effects in the visible and the shortwave infrared spectrum. Using the physics engines within the Blender 3-D graphic design software, physical representations of granular soil scenes were created. Each scene characterized a specific particle distribution and density. Chemical and optical properties of pure quartz and magnetite were assigned to particles in the scene based on particle size. This work presents a model to describe an observed phase-angle dependence of beach sand density. Bidirectional reflectance signatures were simulated for targets of varying size distribution and density. This model provides validation for a phenomenological trade space between density and particle size distribution in complex, heterogeneous soil mixtures. It also confirms the suggestion that directional reflectance signatures can be defined by intimate mixtures that depend on pore spacing. The study demonstrated that by combining realistic target geometry and spectral measurements of pure quartz and magnetite, effects of soil particle size and density could be modeled without functional data fitting or rigorous analysis of material dynamics. This research does not use traditional function-based models for simulation. The combination of realistic geometry, physically viable particle structure, and first-principles ray-tracing enables the ability to represent signature changes that have been observed in experimental observations.

  14. Adjustable virtual pore-size filter for automated sample preparation using acoustic radiation force

    SciTech Connect

    Jung, B; Fisher, K; Ness, K; Rose, K; Mariella, R

    2008-05-22

    We present a rapid and robust size-based separation method for high throughput microfluidic devices using acoustic radiation force. We developed a finite element modeling tool to predict the two-dimensional acoustic radiation force field perpendicular to the flow direction in microfluidic devices. Here we compare the results from this model with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes and compressidensities. These experimental parametric studies also provide insight into the development of an adjustable 'virtual' pore-size filter as well as optimal operating conditions for various microparticle sizes. We demonstrated the separation of Saccharomyces cerevisiae and MS2 bacteriophage using acoustic focusing. The acoustic radiation force did not affect the MS2 viruses, and their concentration profile remained unchanged. With optimized design of our microfluidic flow system we were able to achieve yields of > 90% for the MS2 with > 80% of the S. cerevisiae being removed in this continuous-flow sample preparation device.

  15. Single molecule FRET reveals pore size and opening mechanism of a mechano-sensitive ion channel

    PubMed Central

    Wang, Yong; Liu, Yanxin; DeBerg, Hannah A; Nomura, Takeshi; Hoffman, Melinda Tonks; Rohde, Paul R; Schulten, Klaus; Martinac, Boris; Selvin, Paul R

    2014-01-01

    The mechanosensitive channel of large conductance, which serves as a model system for mechanosensitive channels, has previously been crystallized in the closed form, but not in the open form. Ensemble measurements and electrophysiological sieving experiments show that the open-diameter of the channel pore is >25 Å, but the exact size and whether the conformational change follows a helix-tilt or barrel-stave model are unclear. Here we report measurements of the distance changes on liposome-reconstituted MscL transmembrane α-helices, using a ‘virtual sorting’ single-molecule fluorescence energy transfer. We observed directly that the channel opens via the helix-tilt model and the open pore reaches 2.8 nm in diameter. In addition, based on the measurements, we developed a molecular dynamics model of the channel structure in the open state which confirms our direct observations. DOI: http://dx.doi.org/10.7554/eLife.01834.001 PMID:24550255

  16. Evaluation of borate bioactive glass scaffolds with different pore sizes in a rat subcutaneous implantation model.

    PubMed

    Deliormanli, Aylin M; Liu, Xin; Rahaman, Mohamed N

    2014-01-01

    Borate bioactive glass has been shown to convert faster and more completely to hydroxyapatite and enhance new bone formation in vivo when compared to silicate bioactive glass (such as 45S5 and 13-93 bioactive glass). In this work, the effects of the borate glass microstructure on its conversion to hydroxyapatite (HA) in vitro and its ability to support tissue ingrowth in a rat subcutaneous implantation model were investigated. Bioactive borate glass scaffolds, designated 13-93B3, with a grid-like microstructure and pore widths of 300, 600, and 900 µm were prepared by a robocasting technique. The scaffolds were implanted subcutaneously for 4 weeks in Sprague Dawley rats. Silicate 13-93 glass scaffolds with the same microstructure were used as the control. The conversion of the scaffolds to HA was studied as a function of immersion time in a simulated body fluid. Histology and scanning electron microscopy were used to evaluate conversion of the bioactive glass implants to hydroxyapatite, as well as tissue ingrowth and blood vessel formation in the implants. The pore size of the scaffolds was found to have little effect on tissue infiltration and angiogenesis after the 4-week implantation. PMID:23241965

  17. Langevin granulometry of the particle size distribution

    NASA Astrophysics Data System (ADS)

    Kákay, Attila; Gutowski, M. W.; Takacs, L.; Franco, V.; Varga, L. K.

    2004-06-01

    The problem of deriving the particle size distribution directly from superparamagnetic magnetization curves is studied by three mathematical methods: (1) least-squares deviation with regularization procedure, (2) simulated annealing and (3) genetic algorithm. Software has been developed for the latest versions of all these methods and its performance compared for various models of underlying particle size distributions (Dirac dgr-like, lognormal- and Gaussian-shaped). For single peak distributions all three methods give reasonable and similar results, but for bimodal distributions the genetic algorithm is the only acceptable one. The genetic algorithm is able to recover with the same precision both the lognormal and Gaussian single and double (mixed) model distributions. The sensitivity of the genetic algorithm—the most promising method—to uncertainty of measurements was also tested; correct peak position and its half width were recovered for Gaussian distributions, when the analysed data were contaminated with noise of up to 5% of MS.

  18. Particle Size Distributions in Atmospheric Clouds

    NASA Technical Reports Server (NTRS)

    Paoli, Roberto; Shariff, Karim

    2003-01-01

    In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.

  19. Exponential Size Distribution of von Willebrand Factor

    PubMed Central

    Lippok, Svenja; Obser, Tobias; Müller, Jochen P.; Stierle, Valentin K.; Benoit, Martin; Budde, Ulrich; Schneppenheim, Reinhard; Rädler, Joachim O.

    2013-01-01

    Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications. PMID:24010664

  20. Quantitative multi-scale analysis of mineral distributions and fractal pore structures for a heterogeneous Junger Basin shale

    NASA Astrophysics Data System (ADS)

    Wang, Y. D.; Liu, K. Y.; Yang, Y. S.; Ren, Y. Q.; Hu, T.; Deng, B.; Xiao, T. Q.

    2016-04-01

    Three dimensional (3D) characterization of shales has recently attracted wide attentions in relation to the growing importance of shale oil and gas. Obtaining a complete 3D compositional distribution of shale has proven to be challenging due to its multi-scale characteristics. A combined multi-energy X-ray micro-CT technique and data-constrained modelling (DCM) approach has been used to quantitatively investigate the multi-scale mineral and porosity distributions of a heterogeneous shale from the Junger Basin, northwestern China by sub-sampling. The 3D sub-resolution structures of minerals and pores in the samples are quantitatively obtained as the partial volume fraction distributions, with colours representing compositions. The shale sub-samples from two areas have different physical structures for minerals and pores, with the dominant minerals being feldspar and dolomite, respectively. Significant heterogeneities have been observed in the analysis. The sub-voxel sized pores form large interconnected clusters with fractal structures. The fractal dimensions of the largest clusters for both sub-samples were quantitatively calculated and found to be 2.34 and 2.86, respectively. The results are relevant in quantitative modelling of gas transport in shale reservoirs.

  1. Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene.

    PubMed

    Cui, Xili; Chen, Kaijie; Xing, Huabin; Yang, Qiwei; Krishna, Rajamani; Bao, Zongbi; Wu, Hui; Zhou, Wei; Dong, Xinglong; Han, Yu; Li, Bin; Ren, Qilong; Zaworotko, Michael J; Chen, Banglin

    2016-07-01

    The trade-off between physical adsorption capacity and selectivity of porous materials is a major barrier for efficient gas separation and purification through physisorption. We report control over pore chemistry and size in metal coordination networks with hexafluorosilicate and organic linkers for the purpose of preferential binding and orderly assembly of acetylene molecules through cooperative host-guest and/or guest-guest interactions. The specific binding sites for acetylene are validated by modeling and neutron powder diffraction studies. The energies associated with these binding interactions afford high adsorption capacity (2.1 millimoles per gram at 0.025 bar) and selectivity (39.7 to 44.8) for acetylene at ambient conditions. Their efficiency for the separation of acetylene/ethylene mixtures is demonstrated by experimental breakthrough curves (0.73 millimoles per gram from a 1/99 mixture). PMID:27198674

  2. Intraspecific body size frequency distributions of insects.

    PubMed

    Gouws, E Jeanne; Gaston, Kevin J; Chown, Steven L

    2011-01-01

    Although interspecific body size frequency distributions are well documented for many taxa, including the insects, intraspecific body size frequency distributions (IaBSFDs) are more poorly known, and their variation among mass-based and linear estimates of size has not been widely explored. Here we provide IaBSFDs for 16 species of insects based on both mass and linear estimates and large sample sizes (n ≥ 100). In addition, we review the published IaBSFDs for insects, though doing so is complicated by their under-emphasis in the literature. The form of IaBSFDs can differ substantially between mass-based and linear measures. Nonetheless, in non-social insects they tend to be normally distributed (18 of 27 species) or in fewer instances positively skewed. Negatively skewed distributions are infrequently reported and log transformation readily removes the positive skew. Sexual size dimorphism does not generally cause bimodality in IaBSFDs. The available information on IaBSFDs in the social insects suggests that these distributions are usually positively skewed or bimodal (24 of 30 species). However, only c. 15% of ant genera are polymorphic, suggesting that normal distributions are probably more common, but less frequently investigated. Although only 57 species, representing seven of the 29 orders of insects, have been considered here, it appears that whilst IaBSFDs are usually normal, other distribution shapes can be found in several species, though most notably among the social insects. By contrast, the interspecific body size frequency distribution is typically right-skewed in insects and in most other taxa. PMID:21479214

  3. Intraspecific Body Size Frequency Distributions of Insects

    PubMed Central

    Gouws, E. Jeanne; Gaston, Kevin J.; Chown, Steven L.

    2011-01-01

    Although interspecific body size frequency distributions are well documented for many taxa, including the insects, intraspecific body size frequency distributions (IaBSFDs) are more poorly known, and their variation among mass-based and linear estimates of size has not been widely explored. Here we provide IaBSFDs for 16 species of insects based on both mass and linear estimates and large sample sizes (n≥100). In addition, we review the published IaBSFDs for insects, though doing so is complicated by their under-emphasis in the literature. The form of IaBSFDs can differ substantially between mass-based and linear measures. Nonetheless, in non-social insects they tend to be normally distributed (18 of 27 species) or in fewer instances positively skewed. Negatively skewed distributions are infrequently reported and log transformation readily removes the positive skew. Sexual size dimorphism does not generally cause bimodality in IaBSFDs. The available information on IaBSFDs in the social insects suggests that these distributions are usually positively skewed or bimodal (24 of 30 species). However, only c. 15% of ant genera are polymorphic, suggesting that normal distributions are probably more common, but less frequently investigated. Although only 57 species, representing seven of the 29 orders of insects, have been considered here, it appears that whilst IaBSFDs are usually normal, other distribution shapes can be found in several species, though most notably among the social insects. By contrast, the interspecific body size frequency distribution is typically right-skewed in insects and in most other taxa. PMID:21479214

  4. Modeling the controllable pH-responsive swelling and pore size of networked alginate based biomaterials.

    PubMed

    Chan, Ariel W; Neufeld, Ronald J

    2009-10-01

    Semisynthetic network alginate polymer (SNAP), synthesized by acetalization of linear alginate with di-aldehyde, is a pH-responsive tetrafunctionally linked 3D gel network, and has potential application in oral delivery of protein therapeutics and active biologicals, and as tissue bioscaffold for regenerative medicine. A constitutive polyelectrolyte gel model based on non-Gaussian polymer elasticity, Flory-Huggins liquid lattice theory, and non-ideal Donnan membrane equilibria was derived, to describe SNAP gel swelling in dilute and ionic solutions containing uni-univalent, uni-bivalent, bi-univalent or bi-bi-valent electrolyte solutions. Flory-Huggins interaction parameters as a function of ionic strength and characteristic ratio of alginates of various molecular weights were determined experimentally to numerically predict SNAP hydrogel swelling. SNAP hydrogel swells pronouncedly to 1000 times in dilute solution, compared to its compact polymer volume, while behaving as a neutral polymer with limited swelling in high ionic strength or low pH solutions. The derived model accurately describes the pH-responsive swelling of SNAP hydrogel in acid and alkaline solutions of wide range of ionic strength. The pore sizes of the synthesized SNAP hydrogels of various crosslink densities were estimated from the derived model to be in the range of 30-450 nm which were comparable to that measured by thermoporometry, and diffusion of bovine serum albumin. The derived equilibrium swelling model can characterize hydrogel structure such as molecular weight between crosslinks and crosslinking density, or can be used as predictive model for swelling, pore size and mechanical properties if gel structural information is known, and can potentially be applied to other point-link network polyelectrolytes such as hyaluronic acid gel. PMID:19660810

  5. A titanosilicate molecular sieve with adjustable pores for size-selective adsorption of molecules.

    PubMed

    Kuznicki, S M; Bell, V A; Nair, S; Hillhouse, H W; Jacubinas, R M; Braunbarth, C M; Toby, B H; Tsapatsis, M

    2001-08-16

    Zeolites and related crystalline microporous oxides-tetrahedrally coordinated atoms covalently linked into a porous framework-are of interest for applications ranging from catalysis to adsorption and ion-exchange. In some of these materials (such as zeolite rho) adsorbates, ion-exchange, and dehydration and cation relocation can induce strong framework deformations. Similar framework flexibility has to date not been seen in mixed octahedral/tetrahedral microporous framework materials, a newer and rapidly expanding class of molecular sieves. Here we show that the framework of the titanium silicate ETS-4, the first member of this class of materials, can be systematically contracted through dehydration at elevated temperatures to 'tune' the effective size of the pores giving access to the interior of the crystal. We show that this so-called 'molecular gate' effect can be used to tailor the adsorption properties of the materials to give size-selective adsorbents suitable for commercially important separations of gas mixtures of molecules with similar size in the 4.0 to 3.0 A range, such as that of N2/CH4, Ar/O2 and N2/O2. PMID:11507636

  6. Atomic layer deposition of SIO2 on porous alumina membranes: controlling the pore size and transport properties

    NASA Astrophysics Data System (ADS)

    Velleman, Leonora; Traini, Gerry; Evans, Peter J.; Atanacio, Armand; Shapter, Joe G.; Losic, Dusan

    2008-12-01

    Atomic layer deposition (ALD) of SiO2 onto nanoporous alumina (PA) membranes was investigated with the aim of adjusting the pore size and transport properties. PA membranes from commercial sources with a range of pore diameters (20 nm, 100 nm and 200 nm) were used and modified by atomic layer deposition using tris(tert-butoxy)silanol and water as the precursor couple. By adjusting the number of deposition cycles, the thickness of the conformal silica coating was controlled, reducing the effective pore diameter, and subsequently changing the transport properties of the PA membrane. Silica coated PA membranes with desired pore diameters from <5 nm to 100 nm were fabricated. In addition to the pore size, the transport properties and selectivity of fabricated silica coated PA membranes were controlled by chemical functionalisation using a silane with hydrophobic properties. Structural and chemical properties of modified membranes were studied by dynamic secondary ion mass spectrometry (DSIMS) and scanning electron microscopy (SEM). Spectrophotometric methods were used to evaluate the transport properties and selectivity of silica coated membranes by permeation studies of hydrophobic and hydrophilic organic molecules. The resultant silica/PA membranes with specific surface chemistry and controlled pore size are applicable for molecular separation, cell culture, bioreactors, biosensing and drug delivery.

  7. Magnetite Particle Size Distribution and Pellet Oxidation

    NASA Astrophysics Data System (ADS)

    Cho, Hyeon Jeong; Tang, Ming; Pistorius, Petrus Christiaan

    2014-08-01

    Oxidation of magnetite pellets is commonly performed to prepare strong pellets for ironmaking. This article presents a contribution to quantitative understanding of fundamental pellet oxidation kinetics, based on measured oxidation kinetics of magnetite particles and pellets. The commonly observed "plateau" oxidation behavior is confirmed to be consistent with the effect of very large differences in magnetite particle sizes in the concentrate from which pellets are produced. The magnetite particles range in size from less than a micron to several tens of a microns; changing the size distribution by inert sintering of pellets decreases both the plateau level of oxidation and the specific surface area, in ways that are compatible with an assumed Rosin-Rammler magnetite particle size distribution.

  8. Comparison of drop size distributions from two droplet sizing systems

    NASA Technical Reports Server (NTRS)

    Oldenburg, John R.; Ide, Robert F.

    1990-01-01

    A comparison between the Phase Doppler Particle Analyzer and the combined measurements from Particle Measuring Systems' Forward Scattering Spectrometer Probe and the Optical Array Probe was conducted in an icing wind tunnel using NASA Icing Research Tunnel spray nozzles to produce the supercooled water droplet cloud. Clouds having a range of volume median diameters from 10 to greater than 50 microns were used for the instrument comparisons. A volume median diameter was calculated from combining the droplet distributions of the Optical Array Probe and the Forward Scattering Spectrometer Probe. A comparison of the combined volume median diameters and the Phase Doppler Particle Analyzer volume median diameters showed agreement from 10 microns up to 30 microns. Typical drop size distributions from the Phase Doppler Particle Analyzer, the Forward Scattering Spectrometer Probe, and Optical Array Probe are presented for several median volume diameters. A comparison of the distributions illustrates regions of the distributions where there is good agreement and other regions where there are discrepancies between the Phase Doppler Particle Analyzer and the Particle Measuring Systems' droplet size instruments.

  9. Temperature and pore pressure distribution in a concrete slab during the microwave decontamination process

    SciTech Connect

    Li, W.; Ebadian, M.A.; White, T.L.; Grubb, R.G.; Foster, D. Jr.

    1994-10-01

    As an application of microwave engineering, the new technology of concrete decontamination and decommissioning using microwave energy has been recently developed. The temperature and pore pressure within the concrete are studied theoretically in this paper. The heat and mass transfer within the porous concrete, coupled with temperature dependent dielectric property are investigated. The effects of microwave frequency (f), microwave power intensity (Q{sub 0,ave}), concrete porosity ({phi}) on the temperature and pore pressure distributions and their variations are fully discussed. The effects of the variation of complex dielectric permittivity ({epsilon}) and presentation of different steel reinforcements are also illustrated.

  10. Aerosol and air pollution size distribution

    NASA Astrophysics Data System (ADS)

    Shani, Gad; Haccoun, A.; Kushelevsky, A.

    The size distribution of aerosols was measured in a moderately industrial city, in a semi-arid zone on the Negev desert border. The aerosols in the city of Beer Sheva are from two sources: the dust coming from the desert and urban pollution. The size measurements were done with a cascade impactor. The elemental content of the aerosols was investigated by neutron activation analysis and X-ray fluorescence. The main elements of the dust are: Ca, Si, Fe, Na and the trace elements are: Sc, Se, La, Sm, Hf and others. The main elements of the urban pollution are S, Br, Pb, Cl, Hg and others. It was found that the elements belonging to each group can easily be classified by the size distribution. The analytical consideration of the aerosol size distribution of each group are discussed and two corresponding analytical expressions are suggested. It is shown that aerosols originating in the dust have a hump shape distribution around ~ 4μm, and those originating in urban pollution have a distribution decreasing with increasing aerosol diameter. Many examples are given to prove the conclusions.